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We are working at a site which requires multiple audible and visual alarms to be used in conjunction with a leak detection system . We have been given 24 volt dc beacons and horns by the owner but only have 24 volt ac at the required locations . Has anyone converted economically 24 ac to 24 dc at multiple locations . Each alarm station must be a home run to the machine room .
 

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Straight rectifying of AC to DC gives you rippled DC that is taken from the PEAK of the sine waves, not the RMS voltage. So you end up with a DC voltage level that is 141% of the AC. In this case then just a simple rectifier nets about 34VDC with a lot of ripple. The 24VDC devices may or may not like it, depends on if there are any electronics inside. If they are just incandescent lamps an a piezo buzzer, just putting in a dropping resistor to bring the voltage down to an average closer to 24VDC may be fine (but remember, resistors are heaters). If however they are LEDs and have an internal power supply, you need to check the power supply input requirements and/or check with the mfr to see what it can tolerate. Some DC to DC power supplies do not play well with ripples, they overheat and burn out.

Otherwise, you would need to filter it. Probably easier to just buy a 24VAC to 24VDC power supply.
 
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