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(INPUT VOLTAGE)----[RTOP]-------------(MCU Analog A?)
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[RBOT] --- (Capacitor around 100pF)
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GND GND
It's very easy to get confused in all this for someone who is not sufficiently prepared, like meTalk2 wrote: ↑Jun 12, 2017Hi Paul,
The A7 pin is connected to a voltage resistor, which is "monitoring" the VIN voltage. To prevent any damage/interference with the current circuit, you need to first disconnect the A7 from the voltage divider by disconnecting the JP2, as described here: https://bitbucket.org/talk2/whisper-node-avr/overview#markdown-header-via-solder-jumpers. An alternative would be to use another Analog Pin if they are free.
Additionally, you will need to build your own voltage divider, which I recommend to output 1.1V for the maximum voltage. The reason for that is to use the "INTERNAL" voltage reference present on the MCU. Here an example:
RTOP: 1M
RBOT: 68K
CAP: 100pF (just to provide some stability)
With the relation above you should get 1.1V output when your input is 17.267V. In other words, you can monitor a few volts over 12V you need, which is fine.Code: Select all
(INPUT VOLTAGE)----[RTOP]-------------(MCU Analog A?) | | | | [RBOT] --- (Capacitor around 100pF) | --- | | | | GND GND
Now in the code, you can use the already existent function T2Utils::readVoltage(A?, 0, 17267, 5), where:
A? - this is the analog Pin you going to use
0 - this is the control Pin, it's only necessary if you have a kind of "switch" which will turn the voltage divider ON or OFF - normally used to block the currently leak resistor dividers have. If you use "0" means the function expect the voltage divider to be always "ON", which I think would be the case.
17267 - here you define the Maximum voltage your voltage divider would represent at 1.1V;
5 - finally the number o samples to be collected to be averaged;
Have a look on the Talk2 Example Voltage.Base as reference and the files T2Utils.h and T2Utils.cpp. Otherwise just build your own function to read the analog value (from 0 to 1023) and convert to the voltage it would represent.
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Cheers
I have a problem with voltage conversion. Your explanations have clarified my situation a bit, thank you. I will keep trying. If it doesn't work, I'll ask.I got an Output voltage of 1, 05 V. Isn't that a mistake? I can't find what exactly it is. Any advice is welcome.Talk2 wrote: ↑Jun 12, 2017With the relation above you should get 1.1V output when your input is 17.267V. In other words, you can monitor a few volts over 12V you need, which is fine.
Now in the code, you can use the already existent function T2Utils::readVoltage(A?, 0, 17267, 5), where:
A? - this is the analog Pin you going to use
0 - this is the control Pin, it's only necessary if you have a kind of "switch" which will turn the voltage divider ON or OFF - normally used to block the currently leak resistor dividers have. If you use "0" means the function expect the voltage divider to be always "ON", which I think would be the case.
17267 - here you define the Maximum voltage your voltage divider would represent at 1.1V;
5 - finally the number o samples to be collected to be averaged;
Have a look on the Talk2 Example Voltage.Base as reference and the files T2Utils.h and T2Utils.cpp. Otherwise just build your own function to read the analog value (from 0 to 1023) and convert to the voltage it would represent.
Cheers.