# Temperature Logger and Standalone Voltage Logger

Posted on Feb 6, 2014

Combine the SATL and SAVL together. The schematic was updated with the voltage sensing circuit, I added in a Mosfet so that we only draw power from the voltage source when needed and you`ll notice there are 2 jumpersTemp and Volt. You can switch between logging temperature and voltage by completing the connection of the jumper and modifying a variable

with button presses. // Write to EEPROM if (functionInuse = functionTemperature) { if (dataCount <= eepromMap[eepromMemsize]) {. } } else { if (dataCount <= eepromMap[eepromMemsize] - 1) {. } } I`ll spare you most of the modified code as it just has some if statements as above. There is a new variable called functionInuse which lets us choose between temperature or voltage logging. // Button held down if (buttonPressed = 1) { setup_watchdog(T2S); system_sleep(); if (buttonPressed != 1) { // If button is released after 3 seconds, change delay time. } else { // Change between temperature or voltage logging cbi(GIMSK, PCIE); functionSelect = CONFIGFUNCTION; functionInuse = -1; blinkLed(1, T4S, SKIPLEDOFFDELAY); sbi(GIMSK, PCIE); } } As we did last week, we can calculate the formula which we need to use, 1024 bit / 165 temperature range gives us 6. 206 then we do -40C x 6. 206 gives us our value to minus as 248. The formula is temperature = (value 249) / 6. 206. With voltage logging our maximum voltage is 15V which is a value of 517. All we need to do is divide 517 by 254 for a 1 byte value which gives 2. 035. The formula is voltage = (value 1) * 2. 035) * 0. 001074) * 27. You can download the SATVL_v1. 0_Source which should be used once the v1. 0 PCB is released. At the moment the program size is up to 8028 bytes which is very close to the ATtiny85 program size limit!

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