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kaktus85 / MightyWattR3

Resources for MightyWatt R3 electronic load
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Bias? #2

Open fauks opened 7 months ago

fauks commented 7 months ago

Hello,

I have been using your MightyWatt R3 project to learn how to create my own version.

I am wondering about the "bias" net. Is this a 2.5v or 5v output from the AD5691? It looks like it is fed into the TLV2372 opamp directly after a resistor divider, and the output is the "bias" net. I also see there is a pad on the rear end of the board for "bias" but I'm not sure what it is used for.

Is this correct? Also, if there is a better way to communicate with you, please let me know.

Thank you!

kaktus85 commented 7 months ago

Hi, I am no longer involved in hardware development but as far as I remember, the bias was around 75 mV, derived from the 2.5V reference of the ADC (via R23/R24 divider). The purpose was to offset signals from ground to have a linear response. Even rail-to-rail op-amps are not completely linear at 0 V. But they can be at 75 mV.

po 1. 4. 2024 v 3:28 odesílatel DBC @.***> napsal:

Hello,

I have been using your MightyWatt R3 project to learn how to create my own version.

I am wondering about the "bias" net. Is this a 2.5v or 5v output from the AD5691? It looks like it is fed into the TLV2372 opamp, and the output is the "bias" net.

Is this correct? Also, if there is a better way to communicate with you, please let me know.

Thank you!

— Reply to this email directly, view it on GitHub https://github.com/kaktus85/MightyWattR3/issues/2, or unsubscribe https://github.com/notifications/unsubscribe-auth/ABSVVHL2PLONOSE7S5J4JHTY3CZ4BAVCNFSM6AAAAABFQ4FDQKVHI2DSMVQWIX3LMV43ASLTON2WKOZSGIYTOMZRGU4TOMY . You are receiving this because you are subscribed to this thread.Message ID: @.***>

fauks commented 7 months ago

Thank you! I understand now. I have been beating my head trying to figure out what was going on with the second opamp. I'm learning slowly.

I plan on scaling this up a little and implementing more modern hardware.

fauks commented 7 months ago

One last question, was this designed with the 3.3v logic boards in mind? I thought that is what the VCCIO VREF pin on the shield was used for. I am going to implement a ESP32 and have to figure out what needs to be changed.

kaktus85 commented 7 months ago

Yes, it works with both 3V3 and 5V boards. You are right, the VCCIO / IOREF is exactly that. Voltage at this pin is taken as the digital reference voltage. But the board needs 5V supply to power the fan, relay and DC/DC converter that makes higher voltage for the main transistor.

po 1. 4. 2024 v 14:12 odesílatel DBC @.***> napsal:

One last question, was this designed with the 3.3v logic boards in mind? I thought that is what the VCCIO VREF pin on the shield was used for. I am going to implement a ESP32 and have to figure out what needs to be changed.

— Reply to this email directly, view it on GitHub https://github.com/kaktus85/MightyWattR3/issues/2#issuecomment-2029664745, or unsubscribe https://github.com/notifications/unsubscribe-auth/ABSVVHOXN3HPOJIZTW2V2ZLY3FFK7AVCNFSM6AAAAABFQ4FDQKVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZDAMRZGY3DINZUGU . You are receiving this because you commented.Message ID: @.***>