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| My DIY voltage sensor on board |
Frsky radio system with telemetry enable receiver have an/a couple of analog voltage inputs (for remote voltage measurements). The ER9X Tx software allows the assignment of alarm thresholds to these analog inputs. When the voltage alarm condition occurs a beeper in the R/C Tx sounds off. To use the analog inputs the Rx needs a resistor based attenuator to scale the voltage. The voltage applied to the analog input must not exceed 3.3V, which is the sole purpose of the attenuator.
The attenuator is actually a voltage divider circuit which produce an output voltage that is a fraction of its input voltage. In our case when our flight pack is fully charge (12.6V), the max output of our sensor is 3.3V and getting lower proportionally to our flight pack voltage.
I used the online voltage divider calculator to calculate the resistor, R that i needed for my sensor to give an output of 3.3V when the input voltage is 12.6V. Then i have it simulated in EveryCircuit on my phone.
Only one wire from the sensor is connected to the RX A1/A2 signal pin because the ground is common as our RX and sensor are on the same circuit.
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| Initial calculation done with the help of online voltage devider calculator |
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| Sensor circuit simulated in EveryCircuit for Android |
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| Sensor settings on er9x |
I have to check the true voltage of my flight pack using my trusted multimeter and made adjustment accordingly to my er9x setting to have it show the correct voltage. My A1 is showing my RX voltage which i knew it is unnecessary. But for the sake of having a full telemetry screen, i did include it. A2 is connected to my flight pack.
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| Telemetry display on er9x |
Until now this setup haven't cause me any trouble other than interrupting my flying :)
Please do this at you own risk.
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