Replace batteries with AC source

I would like to replace the (2) AA 1.5 volt batteries with an AC powered source.

I dug up a cell phone charger putting out 5.0 volts at .7 amps.

Would I need to step down the voltage in order to use it for my application?

Thanks, Andy

Reply to
WhiteTea
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Yes, you need to reduce it..

if maybe worth just getting a universal unit from your local hardware store.

But, if you really want to do this, you can use 3 SI diodes in series. 1N4001 or something of that order should do. This will drop the voltage ~ 0.7 volts per unit.

It's not really a good solution but in your case, I don't think you are using it on anything that critical.

The end results should yield ~ 2.9..3.0 volts out..

Reply to
Jamie

I believe in recycling.

I would guess those 3 diodes are way cheaper than a universal unit.

I would also get a chance to show my 5 year old grandson how to solder. :-)

Andy

Reply to
WhiteTea

I believe in recycling.

I would guess those 3 diodes are way cheaper than a universal unit.

I would also get a chance to show my 5 year old grandson how to solder. :-)

Andy

-------------------------------------------------- Andy

Have you measured the output of the 5V source? Some mobile phone chargers have poor regulation and will only output 5V when under load. 3 diodes is good as a cheap way to drop the voltage, but if the 5V is too high in the first place, this could faithfully blow up anything downstream of it.

Alternatively, use an LM317 adjustable regulator. 3 pins - easy to use and bullet proof.

If you can work out resistor values, this will give you a better solution.

Hope this helps

--
Bill Naylor
www.electronworks.co.uk
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Reply to
Electronworks.co.uk

240 ohms for R1 and 330 ohms for R2 gives 2.96 volts.

Ed

Reply to
ehsjr

It puts out 5.0 Volts when connected to my voltmeter. I want to get rid of the batteries for the programmable thermostat.

I am tired of having to reprogram. :-)

Andy

Reply to
WhiteTea

Thanks.

Andy

Reply to
WhiteTea

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The programmable thermostats I've looked at allow 24VAC as an alternative to battery power. (Doorbells, zone controls, thermostats, etc. often run on 24VAC.) Does your thermostat have a manufacturer's name and a model number on it?

--
jiw
Reply to
James Waldby

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