AC TO DC

[cheech]

Need some guidance

I have four of the walther's donkey oil pumps. The operate on DC. I want to power them from the basic xfmr i use for accessories. I have a bridge rectifier....it is an atlas product that is used with its o scale turntable.

Question? Can one bridge rectifier take the AC feed from my accessory 'bus' and feed multiple dc items, like these oil pumps? Or do i need one rectifier for each of the pumps?

thanks in advance

ralph

[chuck]

How much current do the individual devices need and what is the voltage requirement?

What is the current rating for the bridge rectifier you intend to use?

Do any of these devices require smooth dc or can they get by on "ripple dc"? 

[cheech]

The instr from walthers indicate 10 volts for the pump.  The atlas bridge rectifier doesn't have any 'rating' info on it or with the kit it came with. As to smooth DC, the walthers accessory doesn't indicate anything about that.

ralph

[chuck]

OK, device needs 10 volts.  What is the AC input?  A bridge rectifier will convert the AC to DC (ripple DC) but you will lose about 1.4 volts in the conversion. 

Re the current requirements of the device and the current rating of the the rectifier, these are kind of important.  If the bridge's output is less than the required input, the rectifier won't last.  You'd like the bridge's rating to be greater than what is required by the devices.

Ripple effect may not be an issue. 

[phillyreading]

Sounds like an 8 amp bridge rectifier from Radio Shack should work, priced less than $5.00 last time I bought one from Radio Shack.

Also the only way to get pure D.C. that I know of is to use a battery.  Regular batteries are D.C. and capacitors are A.C. storage batteries, realistically there is no A.C. battery.

Lee F.

[cheech]

Thanks Lee

Would i need one rectifier for each of the pumps or would 1 rectifier be able to service all 4?

ralph

[phillyreading]

One 8 amp rectifier should be enuff for 4 pumps unless each is rated over 2 amps, then you would need 2 rectifiers-one for each 2 pumps. The Radio Shack rectifiers are rated at 8 amps 400 volts and will work just as good at lower voltages.

This is what I used on 3 of my Williams locomotives.

Lee F.

[chuck]

If the rectifier can handle the current of all four devices, one is all that is needed.  If you need pure DC (aka no ripple effect) you need to add some components (caps/resistors) to the output circuit to smooth out the waveform and remove the drops.

http://hyperphysics.phy-astr.gsu.edu/hbase/electronic/rectbr.html 

 

[lionelsoni]

The average DC voltage out will be about 90 percent of the AC RMS voltage in, less a little more than a volt from the forward drop of the rectifier diodes.  So, for 10 volts out, you need 12 or 13 volts in.  It might be useful to know that 12.6 volts is a standard power-transformer output.

If the thing you're driving happens to be a lightly loaded permanent-magnet motor, it will behave somewhat like a capacitor and charge to a slightly higher voltage.