Ac to DC Converter
NWCCTV
Posts: 3,629
I am looking to run a Prop and a couple LED's from my doorbell. I believe the doorbell power source is 24v AC. Does anyone know of a small board device to convert the AC to DC?
EDIT:
EDIT:
I should have said LED Matrix's.LED's
Comments
A bridge rectifier, a few filter capacitors, and then a voltage regulator board or DC-to-DC converter of appropriate capacity is likely to do the trick.
The only problem is that the 24VAC is RMS, so the actual peak voltage is 1.414 times higher (about 34 VDC will be output, though the bridge rectifier diodes will drop that a bit). Capacitors and the voltage regulator should expect to handle as least that higher limit as input.
And check the door bell, it may actually be 12VAC... which would make a build a bit easier with the high limit at 17 VDC.
http://www.altronics.com.au/p/m7873-9-36vdc-to-5vdc-regulated-converter/
No, it won't work with a nom 24 vac input.
Technical requirements
- Input voltage range:85~ 265v
- Input current:0.027A(AC110V)
0.0136A(AC220V)
- Input Inrush Current: 20A
- Output voltage range:11.80~12.5V 0~1A
4.90~5.1V 0~1A
- Output power:0 ~18.5 W
- Output efficiency:84%
- Size:7.5*4.0*2.8(cm)
It is quite simple. There are a lot of DC to DC down-converters in the 7 to 48 vdc input range on Ebay. And there are a lot of AC to DC down-converters in the 85 to 265VAC input range.
Regulated Outputs can vary from 12VDC, 9VDC, 5VDC, etc... some are adjustiable or selectible.
So it seems that you either have to insert a bridge rectifier and filter capacitors, or connect to household AC mains. The choice is up to you.
XP Power has a suitable solution for you, but it's a DC-DC converter, with wide (18 to 75 V) input range, fixed output voltage (IM4803SA - 3.3V) and up to 500mA output current (http://www.xppower.com/pdfs/SF_IM.pdf).
There is also a lower range( 9 to 36 V) input option (IM2403SA).
You must only add a suitable bridge rectifier and a filter capacitor at its input.
Digikey has them both in stock at US$14.50, single quantity.
I hope it can fit your needs,
Yanomani
http://www.digikey.com/product-search/en?FV=fff40015%2Cfff8052c&k=bridge+rectifier&mnonly=0&newproducts=0&ColumnSort=0&page=1&stock=0&pbfree=0&rohs=0&quantity=&ptm=0&fid=0&pageSize=25
A 1 amp, 1000 volt SMD bridge rectifier is avaiable for about 9 cents each. Just add some big 50v capacitors, like 22,000mfd or more to reduce ripple. Through hold version seemt to cost more, maybe 50 cents each.
That's what's known as an inverter.
A simple rectifier rectifies one half, one alternation, but still has the same Vpeak considerations. The freq of its output is the line freq.
A bridge rectifies, has output on, both halves. Its output is twice the line frequency.
But if you really want to do this right, you need to calculate how much capacitance you want. I suppose with the input voltage being so high and the regulated voltage being so small, big swings may not be that much of an issue.
NEETS manuals explain how to build these in simple language.. look for the module that explains power supplies.
I am not so sure that one diode and bigger capacitors is cheaper than a bridge rectifier and smaller capacitors. Do anyone want to prove which is cheaper. I can buy 4 1n4007 diodes for next to nothing.
http://www.hnsa.org/doc/
Doesn't cut voltage in half, requires twice the filter capacitance (so its more expensive too as a filter cap is more than
a bridge rectifier). It also adds a DC component to the AC circuit which might cause issues.
The output of a rectifier and no smoothing cap is still DC, even if it's pulsating DC.
So a half-wave rectifier's "average" vs a bridge's doesn't mean so much outside of context.
The difference is the ripple that results with load.
With either method and no load, given filtering/smoothing, the DC levels should be about equal.
The ripple is related to the smoothing cap and the load.
With a half-wave rectifier there's a whole alternation where the cap has to fill the breach.
With a full-wave or a bridge there's a much shorter period where that cap has to hold up.
In practice, a half-wave front-end isn't good for the gas that can be had from a full-wave.
For the same input, more power can be derived from an FWB-based rectifier than from a half-wave.
and sensing the button press on the Processor can be done with an opto-isolator, just use software to determine when the input pulses stop (i.e. over 17 microseconds)
(but then you'll need a separate DC supply to power the microcontroller, but if powering it from the intermittent supply of the doorbell button pushed isn't something I'd do because of contact bounce etc...)
-Phil
AC 85 ~ 265v wide voltage input, high and low voltage isolation, 5v1A\DC12V1A Dual Output Voltage.
In theory, you might be able to just convert the AC to filtered DC, limit the current into the Propeller board and the voltage would drop via the current limiting device (maybe an LM317). I am not sure about it. It may overheat or not stand up under long term use, so I preferred depending on a DC-to-DC step-down module.
The situation is quite simple. The marketplace doesn't manufacture all and everything; it tries to anticipate what is worth keeping in stock. Supplies for AC these days usually eliminate the costly step-down transform and do something else to create a regulated DC at the target range. In the lower voltage range of 48V and below, the presumption is that a DC source from a solar panel or a battery will provide the power.
So you are simply caught in between, where DIY is the best solution. The 24VAC doorbell circuit is a legacy of earlier days.
Well, hey - miss a day, miss a lot.