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taligentx / dscKeybusInterface

An Arduino/esp8266/esp32 library to directly interface with DSC security systems.
GNU General Public License v3.0
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Resistor Selection #258

Closed AKMedi9 closed 2 years ago

AKMedi9 commented 2 years ago

The documentation suggests using a 33k resistor for the clock and read pins for esp8266/esp32 and a 15k resistor for arduino boards. The PCB schematic lists 15k resistor for the NodeMCU board. Is this resistor value critical? Im building a board with an esp32 NodeMCU and I was going to use a 33k resistor here but I just wanted to double check.

Screen Shot 2021-12-16 at 6 33 56 PM Screen Shot 2021-12-16 at 6 35 41 PM

kghandi commented 2 years ago

DSC operates at 12.6V, Arduino at 5V, and ESP at 3.3V. The resistors act as a voltage divider. Vout = Vin R2 / (R1+R2).
So with 10k and 15k we get: Vout = 12.6 10 / 25 = 5.06 good for Arduino And with 10k and 33k: Vout = 12.6 10 / 43 = 2.93 good for ESP

AKMedi9 commented 2 years ago

Thanks that answers my question.