For the sake of argument, let us assume the following First of all, I ended up caving in and doing a full blown 3d model blueprint of the robots entire skeletal structure to scale Hello @devvitltd and welcome to the RobotShop forum! Is Vcc the same as Vcc-? As dBC pointed out, others might have been confused because one of your reasons appears to have gone against established practice. Almost all of the current will be going from your source, through the resistors (R1 & R2) to ground. 
No problems so far (over 3 years), but better power monitoring would be nice. This can also be used to power the Arduino, which is nice. Measuring 12 V via voltage divider: choosing the right resistors, Voltage, current measurement from solar panel using INA219 and ESP-12F, Battery voltage measurement with voltage divider, How to automatically interrupt `Set` with conditions. Finding a suitable multiplexer and its configuration is as difficult as of optocoupler. So higher is better but unfortunately you also need 2) that resistance to be low compared to the input impedance of the analog input. We have an off grid 48V system here as well.
We are using a combination of a voltage divider and an opamp to scale, offset, and isolate the battery voltage from the arduino. Your Vin is 60V and Vout is 3.3V , Assume R1 and R2 have same value, then calculate the values of R1 and R2 using above formula i.e. It's always like that! Referring to standard resistor values, 360K and 5K6 in series will be very close to 64:1 (64.28:1). I'm still not sure about the best way to do this, though. During charging battery voltage can increase to 18 volts. Note: Most ESP8266 development boards come with an internal voltage divider. From automation in big factories handling bread, dough, fish, meats and vegetables to the living room and universities where they still can grip everything you throw on them and still be squishy and safe to be around for students. Although it's in a safe voltage range, the Arduino's impedance varies while sampling, in such a way that the voltage divider's output will be affected. We'll write a follow up with a bill of materials and the design files. Are you able to quantify the effect that lowering the driving impedance to a few tens of ohms had on your readings? How? Relay on off increases response time of voltage monitoring. Digital pins can be reduced by using multiplexers. UL2003 input is connected to multiplexer output. UL2003 input is connected to multiplexer output. Looking forward to getting feedback on our design. Thanks for contributing an answer to Arduino Stack Exchange!
The formula to calculate the output voltage is: I would up R1 to 100kOmega; as it will only result in a 1% error. I have tried creating a voltage divider with 2 resistors but with all values I have tried one resistor almost melts as soon as you connect to battery. Optocouplers also isolates the microcontroller from the battery voltage and provides safety from high spikes. It also has the longest history of robot competition since 1996.
Battery monitoring with 3.3v tolerant microcontroller. First i short circuited the 2 batteries and it cost me much at the end i finally fixed the code and inserted some delays which increased the hardware efficiency. For these boards the input range is 0 to 3.3V. Referring to the ESP8266 Community Forum the analog input imposes a 50nA load, but they also state that the maximum input voltage is only 1V (equivalent to 20 M ohm impedance). Maybe the board you have has different built in scaling. Thats a 23volt range, so to maximize resolution we used a circuit simulator (LTSpice) and adjusted the feedback portion of the opamp to find a configuration that gives us a linear output from the opamp of 0.6V to 3.0V for a 42-65V range. You connect the -input to the output, (turning into a voltage follower), you tie the +input to a defined in-range voltage (which could be + input of the other half - it looks to be as good a place as any, and a by-product of doing that is you have a buffered version of the divided-down battery voltage, should you want it.) @SolarMill, thanks for sharing your progress. A1) Thats actually quite a long runtime for a skid steer robot. I'm watching this too! Basic and the most popular individual battery monitoring technique using microcontrollers in practice is voltage divider circuit. Its obvious from the above discussion that the voltage across Rbottom will not exceed 5 volts now.
If you are interested take the tutorial. Other batteries voltages can be calculated with same method. 2) Give a convenient scaling factor. If the two relays accidentally switched on at the same time their will be a huge blast due to short circuit of batteries. In the above scenario for each battery their must be a dedicated analog channel. I tested a few ESP8266 dev boards I had and to get 1024 on the Analog pin it only requires 3v on all my boards, specs do say 3.3 but all voltages higher than 3 just = 1024 so I will factor this in to my calculations, thank you again! I was making progress though when I had time and want to share my latest progression updates. So it boils down to picking a pair of resistors that Now how to measure voltage of individual batteries connected in series. Aside from the inline fuse lead, which connects to Batt+, all other inputs/outputs are handled by a terminal block at the bottom of the board. If you have any more method in your mind please let me know about it. Two cases are given above when source is at 18 volt and when source is at 12 volt in both the cases the ratio comes out to be constant value. The technique is to measure the voltage across high potential battery first, than against the lower ones and negating the subsequent batteries voltage from the one at higherpotential. The data sheet recommends a source impedance of less than 10 k so that the sample & hold capacitor, which is quite small, charges adequately quickly.
See the DIDRn registers for details. We are also using a stock EmonTX to measure the AC output of our Outback VFX3648Inverter. For example150 watt solar panel outputs 17volts at 6amperesduring full sun, output voltage can even reach above 18 volts. Using an esp8266, how can I create a circuit to measure 2 different analog inputs (not simultaneously) with only one ADC pin available (A0), How to select which resistor is required for my curcuit to reduce voltage. Feeding them Vcc/2 causes them to draw significant current as it means both transistors are on (at least partially) providing a path from Vcc to GND within the buffer (the current draw isn't through the input pin). My test above was just performed on a single part, and the ADCinternal series resistance can varyanywhere from 1K to 100K. Voltage range to be measured = 40 - 65V The major differences between this and the standard Emon setup: So far weve spent the majority of our effort working on the voltage monitoring portion. It only takes a minute to sign up. You need to do a bit more research, either by finding a more detailed data sheet or testing it on the bench with a low voltage source, a meter and a program that loops reporting the ADC output. Since our opamp needs power, we added a 48v-5v DCDC power supply to our design. Were selling off the extras for anyone thats interested. RobotShop, the World's Leading Robot Store For Personal and Professional Robot Technology. So while, dBC, your result falls within my definition of "several times", I restrained myself to "well in excess". For safety, we included an inline fuse thats rated for 125v DC with a value of 315mA. So far this article has been helpful, it talks about a voltage divider with a opamp to get more accuracy, but I need a bit more advice from someone that knows more than myself. RoboCup is the largest scientific annual event to advance A.I., robotics and automation in the world. As soon as we get the boards in from OSH Parkwe'll give an update with how well it works as well asdetails on how to integrate it with the Arduino. I made a simple diy project with the same above logic. Nodemcu Arduino ide is used to write, compile and download the code in nodemcu WiFi module. Relays can also be used to measure voltage across batteries. See http://www.maximintegrated.com/en/app-notes/index.mvp/id/1957. I hope it makes sense to readers about the calculations. So based on the low end of the voltage range the divider chain should total in the region of 45V / 0.1mA = 450K ohms. This means an op-amp buffer is not needed. The higher the battery capacity, the longer it will run, but the more it wil Hi! Arduino relay is used in the project. In parallel combination batteries are connected to increase the shelf life of the source or increase the time of power source to supply suitable voltage to load before needed to be recharged. Note: For the above circuit the resistors values should be selected using the same formula given above. Eventually the voltage monitoring PCB and the Hall effect PCB can be combined into a single unit much like the EmonTX.
This review was automatically translated. Asking for help, clarification, or responding to other answers. Thanks for the additional information and insight. So we can not measure individual battery voltage in this case. Would a 100K resistor connected to ground pull an open analog line down to 0. It would have been nice to actually go a little lower, but I couldnt find lower values at our required voltage rating on DigiKey. Well a little more mathematics is involved here. First i short circuited the 2 batteries and it cost me much at the end i finally fixed the code and inserted some delays which increased the hardware efficiency. ethics of keeping a gift card you won at a raffle at a conference your company sent you to?
We know Vout can be up to maximum 5 volts since nodemcu works and accepts maximum 5 volts at its I/O pins. But in many cases, the cost (I'm including battery life as a potential 'cost') or complications of including an op-amp and providing a power supply are unacceptable or unwarranted. This ratio is utilized in code for predicting the actual source/battery voltage. Now we can find Rtop. You can find many tutorials on internet on how to do so. An additional benefit of the opamp is it isolates the battery side of the circuit from the Arduino. amp's usefulness for scaling and providing the required offset, but I'm surprised you found that the varying input impedance of the multiplexer has a significant effect. JavaScript seems to be disabled in your browser. Cool project!
dk%vGCNm%BUvvt-8 SS2dx0!| )RG%Iy2- 09q ;M)d=zcz GEqXbtA|GX].xz=eB}y(Vgv'x)",(eY~t\^JM~?vd6&h_x:foU({l8!0w/wXVH)eaDg>g:-Wuw,1ale.ksI%kxm7X+3m/dBo="DqLx3#`l0#V!0s}g'sSA%]-T4t} Since most of the OpenEnergyMonitor ecosystem is geared towards grid-tied AC systems, weve spent the past few weeks working on new functionality that will allow us to monitor and log the power and energy readings from our off-grid setup. Four 12 volt batteries are connected in series to output 48 volts. Now if 18 volts are at battery side it will be divided across resistors, 5 volts drops at 10k resistor and remaining 13 volts drops at 26k resistor. Analog multiplexers can also be used instead of relays. Making statements based on opinion; back them up with references or personal experience. I've got a 2560 here that draws 62.5mA on the 5V rail when all inputs are configured as inputs (the power-up default) with nothing connected.
Arduino relay is used in the project. This is where the OPAMP might come into play. But what about if we want to measure an individual battery connected to a cluster of batteries in series or parallel combination. CT clamps will not work with DC. Didn'tto repeat incorrect information, we were justexplaining our design process to the best of our abilities. Was thinking something along the lines of a Raspberry Pi PICO and a bluetooth or WIFI module in each scale which is speaking to an RPI self hosting a wifi network / bluetooth host to receive the data and display it. So voltage divider is used here to divide the voltage in two half while ensuring that the one half voltage can not increase 5 volts in any scenario(charging etc). The battery bank voltage swings from 42V minimum when they are almost empty to 65V maximum when the batteries are being equalized. Thank you very much for putting your time into that answer. Those digital input buffers are at their best when you feed them 0V or Vcc;leavethem floating (or feedthem an analog signal)and they start to suck current. That drops to 42.6mAafterenabling all pull-ups. Vin is 18 volts when the battery is charging(worst case scenario). An extra power some time is also needed to power the optocoupler. Why And How Do My Mind Readers Keep Their Ability Secret. Also, using a voltage divider creates a (small) drain which I would like to avoid. How can I get an AnyDice conditional to convert a sequence to a boolean?
It outputs an equivalent voltage to input but with drop in voltage rating. A few days after sending off the board design for printing I came across some comments in another thread about tying down the unused opampsto reduce noise and power consumption. But if for any reason the battery negative is not earthed, then you have a potentially dangerous situation. Open-source tools for energy monitoring and analysis. 300 or 330 (optional). These calculations will also be suitable for 1/2 Watt and 1 Watt resistors. A typical ADC clock rate is 125kHz, so a conversion takes 104 usecs, the first 12 usecs of which is charging the cap. Both are adressed in the link posted by VE7JRO. To learn more, see our tips on writing great answers. 1/4 Watt resistors are common and easily available so I will base my calculations on that. With an opamp we can focus on the 23 volts that really matter and increase our resolution. How to tell reviewers that I can't update my results. Check out our engineering forums, Getting started with MicroPython on ESP8266, How to use MicroPython with ESP8266 and ESP32 to connect to a WiFi network, Using MicroPython SSD1306 driver to interface an OLED display with ESP8266 & ESP32, How to use ESP8266s sleep modes in MicroPython, MicroPython: Time-related functions, timers & interrupts in ESP8266 and ESP32, MicroPython Reading analog signals in ESP8266 and ESP32, ESP8266/ESP32-based WiFi access point using MicroPython, How to achieve longer MCU battery life with low power sleep mode, Infineons CoolSiC devices support Deltas bi-directional inverter, Qualcomm and Mahindra to provide immersive in-vehicle experiences, Diodes launches high-efficiency synchronous boost converter, Help designing 1.6KW Isolated AC/DC with Constant Current Output, Help with Zero Crossing Detector with the 16F877A code on MPLAB XC8. For example for the above circuit the measured voltage across battery-1 is 48v and battery-2 is 36v. Voltage is divided against the two resistors according to the resistor ohmic values.
Are Banksy's 2018 Paris murals still visible in Paris and if so, where? All with email notifications. Our ultimate goal is a well designedopen source module that anyonecan makefor monitoring their off-grid systems, complete with power supplies for Arduino and accesories (such as Hall effect current sensors). Can I use a MOSFET to connect the voltage divider just before reading the voltage? Double pole single through relays with batteries and microcontroller connections are shown below. Using optocouplers is another way to do the same task. The current through the voltage divider should therefore be at least 2000 * 50nA = 0.1 mA. Arduino Stack Exchange is a question and answer site for developers of open-source hardware and software that is compatible with Arduino. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. User can see the battery status now on smart devices like mobile and desktop computers. Solar charge controller also output voltage approximately equal to 15 volts to charge the batteries. That needs just two wire links on the underside of the PCB. They will draw a maximum of 65V/(360K + 5K6) = 0.18mA and the 360K resistor will dissipate about 10mW. Announcing the Stacks Editor Beta release! It's just that alot of the designs used around here do monitor signals with a source impedance of roughly 10K and with no op-amp between them and the ADC input, so if there were a problem with a 4.7K source impedance, people would rightly want to know more. We can also offset these values so they better fit into the range of the Arduino's inputs. In a state with the common law definition of theft, can you force a store to take cash by "pretending" to steal? When flying from Preclearance airports to the US, do airlines validate your visa before letting you talk to Preclearance agents? With the new TurtleBot 4 Mobile Robot coming soon this fall, the next-generation robotic platform for learning the Robot Operating System (ROS), it's more relevant than ever to take a look back at how the TurtleBot came to life. A linear optocoupler is one which can perform the job at best. Ratio is multiplied with voltage at Rbottom for actual voltage value. Measuring string array of batteries voltages using arduino, The circuit seems to be pretty simple in diagram but their are some serious pros and cons. 1) Are working within their wattage rating. We put our selected components into a PCB design program (Eagle) and after using their automatic routing option, spent a few hours cleaning up the design to make it look pretty. This suggests that you have been using values that are too low. Each relay must be properly switched on and off one by one. Service Time Monday to Friday: 9 AM - 4 PM EST (Eastern Time Zone) 1-866-627-3178 Toll-free (in North America) (Sales Department Only. Thanks. Considering thatthe opamponly cost $2.65, it seemed like a safe route to go with some additional perks along the way. 2.2K Measuring an individual battery voltage or a whole bank of battery using any microcontroller(arduino, microship pic, Avr, Atmega, Intel, NXP, stm32)is an easy task. Low ohm resistors can sunk much current and wires could be heated instantly. We can't feed this output directly to the Arduino though. In the above circuit four voltage divider circuits are used to measure voltage across each battery. The link is below. This is because we used high value resistors in our divider to minimize the wasted power. Similarly if battery-3 is at 23v. What should we do with each of them?
[RYEj,wVn]v9d{{xJ. Lets calculate it. The 0V pinspiked to just over 600mV as it was selected, and then decayed back down to 0V about 3 usecs later, well within the 12 usecsallotted. We just received the PCB boards in the mail and and already found a minor issue with them: the pads for the DCDC supplies are flipped from where they should be (at the opposite edge of the part than where they belong).
Do we just connect the unused pins to ground or do we need a resistor in there? Here are some options: https://www.robotshop.com/en/1-channel- Hey guys Im back!
3) Draw an insignificant amount of current relative to the ratings of the solar panels. I did not have much experience of analog multiplexers i can say any thing more abut them. In our package, we have 3 pins left unconnected: 2out, 2in-, and 2in+. I used ULN2003 relay driver to drive the relay coils. https://openenergymonitor.org/forum-archive/node/11011.html. 47K That wasthe assumption we were operating on, based on comments in other forums about the need for an opampbetween a voltage divider and the analog input pin. As you pointed out, there are additional benefits to the opamp that still justify its usage. Than 36v-23v gives 13v. For higher string of batteries more analog channels are required and microcontrollers usually have 8 analog channels at max. At the end the major drawback is, it still requires a dedicated microcontroller analogchannel to measure each individual battery. like a circuit (from AliExpress) or using some other component that would be greatly appreciated. I selected one resistor Rbottom to be 10k ohm. Heres how people can take their projects from design to completion. * Free shipping is only available for products shipped by RobotShop. The input voltage that will generate the full scale 10 bit encoding (1024) may well be different. Take a look I will discuss circuit its pros and cons below the diagram. Next Steps If battery is not charging and say supplying 12 volts what will be the voltage drop across resistors? Also do isolated DC Current measuring with the ACS 758. Our PCB combines three basic circuits: a voltage divider, anopamp, and a power supply. I appreciate the op. Most importantly, we would like to measure the balance of current in the three major branches of an off grid system: the Solar (always positive), the Load (always negative), and the Battery (+/- depending on the other two). For example for the above circuit the measured voltage across battery-1 is 48v and battery-2 is 36v. Well in excess might be a bit bold, but I think if you stick with the 10K recommendation you should be fine. Standard 1/4 watt resistors are going to melt when overloaded 10 times.
please suggest resistor types (e.g. So battery-2 is supplying 13 volts in series string array. - I would like to have 45 to 60 minute runtime and replaceable if practical. One has to measure mV from these devices so precision is required, and I used a Max 6126 for this. Initially we intended to put large hall effects on each of those three major branches but then realized we only really neededtwo of them (solar & batt) and we can extrapolate the value of the third (Load). Since we're gonna have to get them remade anyway, we can incorporate those changes into the opampwhile we're at it. So standard quarter watt E24 series 1% resistors should be suitable. Q1) Battery?
As long as that limitation is understood and is acceptable, and it is being used at low voltages only, that is probably OK. Our hardware includes 8x Trojan T-105 6v Batteries (~10kWh capacity) in a 48v series configuration, an Outback VFX3648Inverter, an Outback FM80 Charge controller, and 2,300 Watts of Sharp brand solar panels mounted on our roof. Other batteries voltages can be calculated with same method. RobotShop is also a leading force in Robotics Education & Research.
Site design / logo 2022 Stack Exchange Inc; user contributions licensed under CC BY-SA. The first 1.5 ADC clocks (out of a total of 13 for a conversion) charge the sample-n-hold cap.
No problems so far (over 3 years), but better power monitoring would be nice. This can also be used to power the Arduino, which is nice. Measuring 12 V via voltage divider: choosing the right resistors, Voltage, current measurement from solar panel using INA219 and ESP-12F, Battery voltage measurement with voltage divider, How to automatically interrupt `Set` with conditions. Finding a suitable multiplexer and its configuration is as difficult as of optocoupler. So higher is better but unfortunately you also need 2) that resistance to be low compared to the input impedance of the analog input. We have an off grid 48V system here as well. We are using a combination of a voltage divider and an opamp to scale, offset, and isolate the battery voltage from the arduino. Your Vin is 60V and Vout is 3.3V , Assume R1 and R2 have same value, then calculate the values of R1 and R2 using above formula i.e. It's always like that! Referring to standard resistor values, 360K and 5K6 in series will be very close to 64:1 (64.28:1). I'm still not sure about the best way to do this, though. During charging battery voltage can increase to 18 volts. Note: Most ESP8266 development boards come with an internal voltage divider. From automation in big factories handling bread, dough, fish, meats and vegetables to the living room and universities where they still can grip everything you throw on them and still be squishy and safe to be around for students. Although it's in a safe voltage range, the Arduino's impedance varies while sampling, in such a way that the voltage divider's output will be affected. We'll write a follow up with a bill of materials and the design files. Are you able to quantify the effect that lowering the driving impedance to a few tens of ohms had on your readings? How? Relay on off increases response time of voltage monitoring. Digital pins can be reduced by using multiplexers. UL2003 input is connected to multiplexer output. UL2003 input is connected to multiplexer output. Looking forward to getting feedback on our design. Thanks for contributing an answer to Arduino Stack Exchange!
The formula to calculate the output voltage is: I would up R1 to 100kOmega; as it will only result in a 1% error. I have tried creating a voltage divider with 2 resistors but with all values I have tried one resistor almost melts as soon as you connect to battery. Optocouplers also isolates the microcontroller from the battery voltage and provides safety from high spikes. It also has the longest history of robot competition since 1996.
Battery monitoring with 3.3v tolerant microcontroller. First i short circuited the 2 batteries and it cost me much at the end i finally fixed the code and inserted some delays which increased the hardware efficiency. For these boards the input range is 0 to 3.3V. Referring to the ESP8266 Community Forum the analog input imposes a 50nA load, but they also state that the maximum input voltage is only 1V (equivalent to 20 M ohm impedance). Maybe the board you have has different built in scaling. Thats a 23volt range, so to maximize resolution we used a circuit simulator (LTSpice) and adjusted the feedback portion of the opamp to find a configuration that gives us a linear output from the opamp of 0.6V to 3.0V for a 42-65V range. You connect the -input to the output, (turning into a voltage follower), you tie the +input to a defined in-range voltage (which could be + input of the other half - it looks to be as good a place as any, and a by-product of doing that is you have a buffered version of the divided-down battery voltage, should you want it.) @SolarMill, thanks for sharing your progress. A1) Thats actually quite a long runtime for a skid steer robot. I'm watching this too! Basic and the most popular individual battery monitoring technique using microcontrollers in practice is voltage divider circuit. Its obvious from the above discussion that the voltage across Rbottom will not exceed 5 volts now.
If you are interested take the tutorial. Other batteries voltages can be calculated with same method. 2) Give a convenient scaling factor. If the two relays accidentally switched on at the same time their will be a huge blast due to short circuit of batteries. In the above scenario for each battery their must be a dedicated analog channel. I tested a few ESP8266 dev boards I had and to get 1024 on the Analog pin it only requires 3v on all my boards, specs do say 3.3 but all voltages higher than 3 just = 1024 so I will factor this in to my calculations, thank you again! I was making progress though when I had time and want to share my latest progression updates. So it boils down to picking a pair of resistors that Now how to measure voltage of individual batteries connected in series. Aside from the inline fuse lead, which connects to Batt+, all other inputs/outputs are handled by a terminal block at the bottom of the board. If you have any more method in your mind please let me know about it. Two cases are given above when source is at 18 volt and when source is at 12 volt in both the cases the ratio comes out to be constant value. The technique is to measure the voltage across high potential battery first, than against the lower ones and negating the subsequent batteries voltage from the one at higherpotential. The data sheet recommends a source impedance of less than 10 k so that the sample & hold capacitor, which is quite small, charges adequately quickly.
See the DIDRn registers for details. We are also using a stock EmonTX to measure the AC output of our Outback VFX3648Inverter. For example150 watt solar panel outputs 17volts at 6amperesduring full sun, output voltage can even reach above 18 volts. Using an esp8266, how can I create a circuit to measure 2 different analog inputs (not simultaneously) with only one ADC pin available (A0), How to select which resistor is required for my curcuit to reduce voltage. Feeding them Vcc/2 causes them to draw significant current as it means both transistors are on (at least partially) providing a path from Vcc to GND within the buffer (the current draw isn't through the input pin). My test above was just performed on a single part, and the ADCinternal series resistance can varyanywhere from 1K to 100K. Voltage range to be measured = 40 - 65V The major differences between this and the standard Emon setup: So far weve spent the majority of our effort working on the voltage monitoring portion. It only takes a minute to sign up. You need to do a bit more research, either by finding a more detailed data sheet or testing it on the bench with a low voltage source, a meter and a program that loops reporting the ADC output. Since our opamp needs power, we added a 48v-5v DCDC power supply to our design. Were selling off the extras for anyone thats interested. RobotShop, the World's Leading Robot Store For Personal and Professional Robot Technology. So while, dBC, your result falls within my definition of "several times", I restrained myself to "well in excess". For safety, we included an inline fuse thats rated for 125v DC with a value of 315mA. So far this article has been helpful, it talks about a voltage divider with a opamp to get more accuracy, but I need a bit more advice from someone that knows more than myself. RoboCup is the largest scientific annual event to advance A.I., robotics and automation in the world. As soon as we get the boards in from OSH Parkwe'll give an update with how well it works as well asdetails on how to integrate it with the Arduino. I made a simple diy project with the same above logic. Nodemcu Arduino ide is used to write, compile and download the code in nodemcu WiFi module. Relays can also be used to measure voltage across batteries. See http://www.maximintegrated.com/en/app-notes/index.mvp/id/1957. I hope it makes sense to readers about the calculations. So based on the low end of the voltage range the divider chain should total in the region of 45V / 0.1mA = 450K ohms. This means an op-amp buffer is not needed. The higher the battery capacity, the longer it will run, but the more it wil Hi! Arduino relay is used in the project. In parallel combination batteries are connected to increase the shelf life of the source or increase the time of power source to supply suitable voltage to load before needed to be recharged. Note: For the above circuit the resistors values should be selected using the same formula given above. Eventually the voltage monitoring PCB and the Hall effect PCB can be combined into a single unit much like the EmonTX.
This review was automatically translated. Asking for help, clarification, or responding to other answers. Thanks for the additional information and insight. So we can not measure individual battery voltage in this case. Would a 100K resistor connected to ground pull an open analog line down to 0. It would have been nice to actually go a little lower, but I couldnt find lower values at our required voltage rating on DigiKey. Well a little more mathematics is involved here. First i short circuited the 2 batteries and it cost me much at the end i finally fixed the code and inserted some delays which increased the hardware efficiency. ethics of keeping a gift card you won at a raffle at a conference your company sent you to?
We know Vout can be up to maximum 5 volts since nodemcu works and accepts maximum 5 volts at its I/O pins. But in many cases, the cost (I'm including battery life as a potential 'cost') or complications of including an op-amp and providing a power supply are unacceptable or unwarranted. This ratio is utilized in code for predicting the actual source/battery voltage. Now we can find Rtop. You can find many tutorials on internet on how to do so. An additional benefit of the opamp is it isolates the battery side of the circuit from the Arduino. amp's usefulness for scaling and providing the required offset, but I'm surprised you found that the varying input impedance of the multiplexer has a significant effect. JavaScript seems to be disabled in your browser. Cool project!
dk%vGCNm%BUvvt-8 SS2dx0!| )RG%Iy2- 09q ;M)d=zcz GEqXbtA|GX].xz=eB}y(Vgv'x)",(eY~t\^JM~?vd6&h_x:foU({l8!0w/wXVH)eaDg>g:-Wuw,1ale.ksI%kxm7X+3m/dBo="DqLx3#`l0#V!0s}g'sSA%]-T4t} Since most of the OpenEnergyMonitor ecosystem is geared towards grid-tied AC systems, weve spent the past few weeks working on new functionality that will allow us to monitor and log the power and energy readings from our off-grid setup. Four 12 volt batteries are connected in series to output 48 volts. Now if 18 volts are at battery side it will be divided across resistors, 5 volts drops at 10k resistor and remaining 13 volts drops at 26k resistor. Analog multiplexers can also be used instead of relays. Making statements based on opinion; back them up with references or personal experience. I've got a 2560 here that draws 62.5mA on the 5V rail when all inputs are configured as inputs (the power-up default) with nothing connected.
Arduino relay is used in the project. This is where the OPAMP might come into play. But what about if we want to measure an individual battery connected to a cluster of batteries in series or parallel combination. CT clamps will not work with DC. Didn'tto repeat incorrect information, we were justexplaining our design process to the best of our abilities. Was thinking something along the lines of a Raspberry Pi PICO and a bluetooth or WIFI module in each scale which is speaking to an RPI self hosting a wifi network / bluetooth host to receive the data and display it. So voltage divider is used here to divide the voltage in two half while ensuring that the one half voltage can not increase 5 volts in any scenario(charging etc). The battery bank voltage swings from 42V minimum when they are almost empty to 65V maximum when the batteries are being equalized. Thank you very much for putting your time into that answer. Those digital input buffers are at their best when you feed them 0V or Vcc;leavethem floating (or feedthem an analog signal)and they start to suck current. That drops to 42.6mAafterenabling all pull-ups. Vin is 18 volts when the battery is charging(worst case scenario). An extra power some time is also needed to power the optocoupler. Why And How Do My Mind Readers Keep Their Ability Secret. Also, using a voltage divider creates a (small) drain which I would like to avoid. How can I get an AnyDice conditional to convert a sequence to a boolean?
It outputs an equivalent voltage to input but with drop in voltage rating. A few days after sending off the board design for printing I came across some comments in another thread about tying down the unused opampsto reduce noise and power consumption. But if for any reason the battery negative is not earthed, then you have a potentially dangerous situation. Open-source tools for energy monitoring and analysis. 300 or 330 (optional). These calculations will also be suitable for 1/2 Watt and 1 Watt resistors. A typical ADC clock rate is 125kHz, so a conversion takes 104 usecs, the first 12 usecs of which is charging the cap. Both are adressed in the link posted by VE7JRO. To learn more, see our tips on writing great answers. 1/4 Watt resistors are common and easily available so I will base my calculations on that. With an opamp we can focus on the 23 volts that really matter and increase our resolution. How to tell reviewers that I can't update my results. Check out our engineering forums, Getting started with MicroPython on ESP8266, How to use MicroPython with ESP8266 and ESP32 to connect to a WiFi network, Using MicroPython SSD1306 driver to interface an OLED display with ESP8266 & ESP32, How to use ESP8266s sleep modes in MicroPython, MicroPython: Time-related functions, timers & interrupts in ESP8266 and ESP32, MicroPython Reading analog signals in ESP8266 and ESP32, ESP8266/ESP32-based WiFi access point using MicroPython, How to achieve longer MCU battery life with low power sleep mode, Infineons CoolSiC devices support Deltas bi-directional inverter, Qualcomm and Mahindra to provide immersive in-vehicle experiences, Diodes launches high-efficiency synchronous boost converter, Help designing 1.6KW Isolated AC/DC with Constant Current Output, Help with Zero Crossing Detector with the 16F877A code on MPLAB XC8. For example for the above circuit the measured voltage across battery-1 is 48v and battery-2 is 36v. Voltage is divided against the two resistors according to the resistor ohmic values.
Are Banksy's 2018 Paris murals still visible in Paris and if so, where? All with email notifications. Our ultimate goal is a well designedopen source module that anyonecan makefor monitoring their off-grid systems, complete with power supplies for Arduino and accesories (such as Hall effect current sensors). Can I use a MOSFET to connect the voltage divider just before reading the voltage? Double pole single through relays with batteries and microcontroller connections are shown below. Using optocouplers is another way to do the same task. The current through the voltage divider should therefore be at least 2000 * 50nA = 0.1 mA. Arduino Stack Exchange is a question and answer site for developers of open-source hardware and software that is compatible with Arduino. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. User can see the battery status now on smart devices like mobile and desktop computers. Solar charge controller also output voltage approximately equal to 15 volts to charge the batteries. That needs just two wire links on the underside of the PCB. They will draw a maximum of 65V/(360K + 5K6) = 0.18mA and the 360K resistor will dissipate about 10mW. Announcing the Stacks Editor Beta release! It's just that alot of the designs used around here do monitor signals with a source impedance of roughly 10K and with no op-amp between them and the ADC input, so if there were a problem with a 4.7K source impedance, people would rightly want to know more. We can also offset these values so they better fit into the range of the Arduino's inputs. In a state with the common law definition of theft, can you force a store to take cash by "pretending" to steal? When flying from Preclearance airports to the US, do airlines validate your visa before letting you talk to Preclearance agents? With the new TurtleBot 4 Mobile Robot coming soon this fall, the next-generation robotic platform for learning the Robot Operating System (ROS), it's more relevant than ever to take a look back at how the TurtleBot came to life. A linear optocoupler is one which can perform the job at best. Ratio is multiplied with voltage at Rbottom for actual voltage value. Measuring string array of batteries voltages using arduino, The circuit seems to be pretty simple in diagram but their are some serious pros and cons. 1) Are working within their wattage rating. We put our selected components into a PCB design program (Eagle) and after using their automatic routing option, spent a few hours cleaning up the design to make it look pretty. This suggests that you have been using values that are too low. Each relay must be properly switched on and off one by one. Service Time Monday to Friday: 9 AM - 4 PM EST (Eastern Time Zone) 1-866-627-3178 Toll-free (in North America) (Sales Department Only. Thanks. Considering thatthe opamponly cost $2.65, it seemed like a safe route to go with some additional perks along the way. 2.2K Measuring an individual battery voltage or a whole bank of battery using any microcontroller(arduino, microship pic, Avr, Atmega, Intel, NXP, stm32)is an easy task. Low ohm resistors can sunk much current and wires could be heated instantly. We can't feed this output directly to the Arduino though. In the above circuit four voltage divider circuits are used to measure voltage across each battery. The link is below. This is because we used high value resistors in our divider to minimize the wasted power. Similarly if battery-3 is at 23v. What should we do with each of them?
[RYEj,wVn]v9d{{xJ. Lets calculate it. The 0V pinspiked to just over 600mV as it was selected, and then decayed back down to 0V about 3 usecs later, well within the 12 usecsallotted. We just received the PCB boards in the mail and and already found a minor issue with them: the pads for the DCDC supplies are flipped from where they should be (at the opposite edge of the part than where they belong).
Do we just connect the unused pins to ground or do we need a resistor in there? Here are some options: https://www.robotshop.com/en/1-channel- Hey guys Im back!
3) Draw an insignificant amount of current relative to the ratings of the solar panels. I did not have much experience of analog multiplexers i can say any thing more abut them. In our package, we have 3 pins left unconnected: 2out, 2in-, and 2in+. I used ULN2003 relay driver to drive the relay coils. https://openenergymonitor.org/forum-archive/node/11011.html. 47K That wasthe assumption we were operating on, based on comments in other forums about the need for an opampbetween a voltage divider and the analog input pin. As you pointed out, there are additional benefits to the opamp that still justify its usage. Than 36v-23v gives 13v. For higher string of batteries more analog channels are required and microcontrollers usually have 8 analog channels at max. At the end the major drawback is, it still requires a dedicated microcontroller analogchannel to measure each individual battery. like a circuit (from AliExpress) or using some other component that would be greatly appreciated. I selected one resistor Rbottom to be 10k ohm. Heres how people can take their projects from design to completion. * Free shipping is only available for products shipped by RobotShop. The input voltage that will generate the full scale 10 bit encoding (1024) may well be different. Take a look I will discuss circuit its pros and cons below the diagram. Next Steps If battery is not charging and say supplying 12 volts what will be the voltage drop across resistors? Also do isolated DC Current measuring with the ACS 758. Our PCB combines three basic circuits: a voltage divider, anopamp, and a power supply. I appreciate the op. Most importantly, we would like to measure the balance of current in the three major branches of an off grid system: the Solar (always positive), the Load (always negative), and the Battery (+/- depending on the other two). For example for the above circuit the measured voltage across battery-1 is 48v and battery-2 is 36v. Well in excess might be a bit bold, but I think if you stick with the 10K recommendation you should be fine. Standard 1/4 watt resistors are going to melt when overloaded 10 times.
please suggest resistor types (e.g. So battery-2 is supplying 13 volts in series string array. - I would like to have 45 to 60 minute runtime and replaceable if practical. One has to measure mV from these devices so precision is required, and I used a Max 6126 for this. Initially we intended to put large hall effects on each of those three major branches but then realized we only really neededtwo of them (solar & batt) and we can extrapolate the value of the third (Load). Since we're gonna have to get them remade anyway, we can incorporate those changes into the opampwhile we're at it. So standard quarter watt E24 series 1% resistors should be suitable. Q1) Battery?
As long as that limitation is understood and is acceptable, and it is being used at low voltages only, that is probably OK. Our hardware includes 8x Trojan T-105 6v Batteries (~10kWh capacity) in a 48v series configuration, an Outback VFX3648Inverter, an Outback FM80 Charge controller, and 2,300 Watts of Sharp brand solar panels mounted on our roof. Other batteries voltages can be calculated with same method. RobotShop is also a leading force in Robotics Education & Research.
Site design / logo 2022 Stack Exchange Inc; user contributions licensed under CC BY-SA. The first 1.5 ADC clocks (out of a total of 13 for a conversion) charge the sample-n-hold cap.