Does the emonTx Shield need an actual Arduino?

Hardware emonTx
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122

Hi Robert
I’m trying to get my head around which bias to connect the diodes, wouldn’t you connect them in parallel reversed bias so one conducts on each cycle?

Regards
Dave

123

No! If you did, the pair would clip at 0.7 V. Whichever way round the voltage is, one always conducts at 0.7 V, the other doesn’t get a look-in.

If they are in series but facing opposite ways, one conducts at its zener voltage and the other conducts at 0.7 V. With the polarity to the pair reversed, the first conducts at 0.7 V and the second at its zener voltage. Result: they clip either way at (zener voltage + 0.7 V).

124

Thanks Robert, that makes sense as were interested in the reverse bias breaking down at the required voltage.

Regards
Dave

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A post was merged into an existing topic: Serial-Direct connection between Pi and emonTx shield