insideGadgets

Following from Part 2 we configured our op-amp and tested to make sure it worked like we wanted it to. Now it’s time to test logging the op-amp’s output using the ATtiny’s ADC, storing the results in the ATtiny’s SRAM and transferring this to the PC.

Here is the current schematic.

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ADC Prescaler / Interrupt

Before we continue, previously I based my assumption of the ADC conversion only taking 65us when at 200KHz however if we use the ATtiny’s internal oscillator for CPU clock speeds (1Mhz, 2Mhz, 4Mhz, etc) there is no ADC clock division / CPU clock combination that will give us 200KHz.

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The Standalone Temperature/Voltage Logger v1.0 has now been released. Download SATVL v1.0 or view the Standalone Temperature/Voltage Logger project page. In the download, I’ve include a PDF guide file that has everything you need including step by step assembly instructions with pictures.

After about a months wait I’ve received 10 boards from Itleadstudio, they look good and I have successfully built a board up and it’s working. The SATVL is not currently up for sale at the moment until I receive a few more parts I’m expecting which should be in about 1-2 weeks.

During the testing process I found a few problems and a design flaw that made it to the PCB however it’s correctable and still functions as it should.

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Following on from Part 1, we built our op-amp circuit and now it’s time to test it out. I ordered both the LM358 and OPA333 and began by testing the circuit on the LM358 as it was a DIP part.

I was powering the circuit from a 3V battery and was seeing something very strange; the output was 1.97V with no load connected.

It didn’t seem to match the circuit diagram above.

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