# powering many solenoids

#### kballing

Joined Jun 18, 2007
18
In the past I built a serial controlled relay board to control my Christmas lights with my computer. I plan on using the same board to control solenoids that bang on metal bars to make music. I have come by 30+ large solenoids that take about 20VA each to trigger correctly. My problem is this: How do I supply power to them so that I can trigger more than one at a time?

As it stands, my relay boards only work with AC power. It wouldn't be practical to have a transformer for every solenoid. Is there a way I can have one power supply and a way to have the right amount of power go to each solenoid regardless of how many are connected?

If it makes a difference, I can put together new relay boards that use DC.

Wouldn't I essentially need a beefy resistor for each solenoid to limit the current through each one?

#### hgmjr

Joined Jan 28, 2005
9,029
Do you have a schematic of the circurtry as it now exists?

We could then take a look and see what changes could be made so that it meet your new requirements.

hgmjr

#### mik3

Joined Feb 4, 2008
4,843
You can use a big transformer to power all the solenoids. Its power rating should be 20VA*(number of solenoids turned on the same time).

#### kballing

Joined Jun 18, 2007
18
The biggest cheap wall transformer that I can seem to find is 24V@2A. What's the difference between a normal transformer and a current transformer? There seems to be a larger variety of current transformers with larger power outputs.

I need enough power to drive multiple solenoids (4 or more), while only allowing the right amount of power when only one is on.

Wouldn't I need something like a really high power resistor?

What if while only one note was on I also triggered on a lightbulb or something in parallel? Wouldn't that split the current? Then I could turn on zero, one, two, or three bulbs depending on how many solenoids are triggered.

#### mik3

Joined Feb 4, 2008
4,843
Can you post a circuit of what exactly you want to do and the voltage and current requirements of the components?

#### kballing

Joined Jun 18, 2007
18
Not very complicated. Triacs act as a switch to trigger each solenoid. the loads are in parallel, and there is an AC supply. The solenoids take approx. 20VA each and I want to be able to power on one or two or all of them without having too much or too little power going to each. What do I insert to do this?

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#### mik3

Joined Feb 4, 2008
4,843
If each solenoid needs 20VA the multiply it by the number of the solenoids to get the total power (in case they are all turned on). You will need a transformer rated at the total power you calculated before. This power rating depends on how many solenoids will be on the same time. If you use a transformer which outputs the rated voltage of the solenoids then its fine, each solenoid will draw the power it needs independently of the others.