Hello fellow impthusiasts
I want to upgrade the nora so that I can connect external wired analog sensors to it. I will be using1/8" stereo phone jack connectors.
The analog sensors I am currently using has 3 pins: VCC, GND and signal. Output signal is 0-3V. Supply voltage 3.3-20V
I have attached my schematic. The block ‘Analog sensor input circuit’ is the one I added. I haven’t altered anything else in the original schematic.
Should i use the ‘VBAT/3V0’ directly from the boost converter or the ‘3V0_sensor’ from the powergate to supply my analog sensors?
I love the idea of hooking up those sensors up.
Here’s a couple suggestions:
- You should adjust the power supply feedback network (R15/16) to get 3V3 out which is required by the VH400.
- You should use 3V0_SENSOR for both the sensors themselves (as you have already done) and the input op-amps (U80).
- Not all the pins on the imp have ADCs, you have several analog signals connected to non-analog capable pins. You will need to re-arrange which pins are connected to what, but things like SENSOR_EN_L don’t need to be on ADC-capable pins which they currently are.
- I do not think your op-amp circuit will do what you want it to do, you should go back and check. Likewise, your protection needs to be on the input signal itself.
- U4 appears to be un-powered.
Hope you find this feedback helpful. Good luck!
Thanks for the informative and very helpfull reply!
I attached a new schematic.
Regarding to the boost converter data-sheet, the current configuration of R15 = 270k and R16 = 43k should give 3,3V. From the datasheet: VOUT1 = 0.45 × (270k+43k ) / 43k = 3.276V. Or have i missed something?
thanks will do that, can you explain why so i might learn?
Thanks i have fixed it. Moved the SENSOR_EN_L as suggested and reduced so I only have 3 inputs, utilizing card pin2, 10 and 11. I am not sure how the ‘sensor_drain’ on card pin 5 works, so i am not sure if it needs ADC, and hence i did not re-asign it.
Duh what a blunder on my part. The sensor signal should have been connected to ‘+’ on the op-amp and not to ‘-’. I think it is configured corretly now, or am i still mistaken?
I was to hasty in uploading the last PDF schematic (i forgot to configure the unused op-amp).
I have attached a new pdf here.