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Author: Subject: Balance repair
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[*] posted on 25-11-2020 at 12:40


That circuit is a bit scary, but most of it is irrelevant.

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[*] posted on 25-11-2020 at 15:04


That circuit looks like a slightly different sensing principle. The LED appears to be regulated by feedback from one of the photodiodes, probably to set up a fixed light level for the other photodiode. The photodiode with the 'flag' is part of the servo loop that drives the motor (a torque motor - same sort of thing as drives the heads in a hard drive). It does not appear to look for light balance between the two photodiodes, but rather maintain a fixed light level on one photodiode.
The rest of it is a current to voltage converter to turn the motor current into a voltage for the digital meter.
Not scary at all :D (apart from the 741 opamps - those are virtually museum pieces)




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[*] posted on 2-12-2020 at 11:56




I see this module on ebay.

https://www.ebay.co.uk/itm/DS1256-24-Bit-8-Channel-ADC-AD-Mo...

It has an SPI interface.
I will have to start reading up on that . A raspberry pie has SPI. Is it as simply as connecting any SPI interface readout device to the A to D converter?
For example this item?

https://www.ebay.co.uk/itm/Waveshare-2-23Inch-OLED-Display-H...


Also the A to D converter is only good for signals as high as three volts (2 volts below the devices supply voltage which is 5 volts).
The higher the voltage I am measureing accross the 'output' resistor (the resistor mesureing the current) the better. It gives better resolution reading 1 to 15v (say) that 0 to3 volts.

TFYT

Yob
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[*] posted on 3-12-2020 at 01:48


As long as you remember that resolution and accuracy are not the same thing.



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