24VAC Transformer from Air Handler, 7805


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  1. #1
    Join Date
    Feb 2009
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    26

    Default 24VAC Transformer from Air Handler, 7805

    Hi All,
    I recently put together my own thermostat for my home running a heat pump. I bread boarded the whole device and tested with a 9VAC transformer and everything works as expected. Upon doing a test hook up to the 24VAC transformer (the air handler uses for the control relays) the voltage after my 7805 is roughly over 1 volt instead of 5 volts. I am attaching a schematic.

    Basically I take the 24VAC output from the transformer and put it throught a full wave bridge rectifier. On the output of the rectifier I have a 1000uf and a 100uf cap. Right before the 7805 regulator on the input I have a 0.33uf ceramic cap. On the output pin I have a 0.1uf ceramic cap followed by a 470uf cap.

    I can't seem to get my regulator to put out 5V off of the 24VAC Transformer.

    Any suggestions or troubleshooting tips will be greatly appreciated.

    Thanks,
    Nemesis
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