Really easy question regarding reducing and changing wall voltage

Thread Starter


Joined Jun 8, 2008
Hi guys, this is gonna be a real easy question for most of you I'm sure but I'm really new to electronics and need your help! I have a rotary solenoid which I am planning to use at some point in the future for a specific task. It is suitable for continuous use at 24Vdc drawing 0.79 amps and it is possible to increase the voltage up to 110Vdc with a much lower duty cycle. Now I have never plugged anything into a wall before (and don't plan on doing so until I have done allot more research!) but I was wondering how you would suggest that I go about plugging this thing in?! How do I convert the standard UK 240v AC to 24Vdc? Also if I want to vary the voltage from 24Vdc up to 110Vdc how would you recommend that I did this? :confused: Sorry for my ignorance but like I said I am only just getting started! :)


Joined Feb 4, 2008
Well, if you are unfamiliar with the mains supply I suggest you not to experiment, its dangerous. Its better to buy a ready one 240VAC/24VDC power supply and make your job safely. Also, if it works with 24VDC why you want to make the voltage higher which is something dangerous if you dont know how to deal with it. What is more, you will need a DC chopper circuit to use a higher voltage to power the coil. Is there a reason of using a higher voltage?


Joined Apr 20, 2004
If you can find a step down transformer that puts out 18 volts, the DC output will be right at 24 after rectification and filtering. 110 VDC tends to be lethal. I would recommend against playing around with higher voltages. Anything that has terminals exposed that carry voltages above 24 volts should be treated as potential shock hazards.


Joined Aug 7, 2008
First: Be caefull, 240 can hurt. Use a 100 W,240 to 110V step-down transformer, follow with 1 A Variac connected to a 1 A bridge rectifier, add a little bit of filtering[1000 μF]and you can go from 0 to 125 V almost DC.

Thread Starter


Joined Jun 8, 2008
Hi guys, thanks very much for the replies and also for the warnings! Firstly, don't worry, I am not going to plug anything in for a very long time. I have a 2yr old son, a good job and everything to live for at the moment so I am being very cautious with this! The project that I am doing has been on the cards for a while, I have been steadily researching for several months and don't suppose I will plug anything in for a few months yet and when I do it will be at low voltages! I have another post which I placed a few months ago which I have just bumped up to get more feedback on and it out lines my project thus:

My background is that of a creative music technologist, I design software and musical instrument interfaces. I have had the idea of creating a drum kit that is played with solenoids triggered by complex MIDI patterns and knew that I would have to be at least a little acquainted with electronics to accomplish this! Luckily most of the hard work has been done for me in the form of the fantastic MIDItron interface which allows you to output a voltage in response to MIDI data through 1 of 20 output terminals. They even give a fairly simple schematic for wiring up solenoids in conjunction with a transistor wired up to the MIDItron terminal which I have included below:

Now as you can see I am trying to simulate the actions of a live drummer which is why I eventually want to eventually be able to regulate the supply voltage, so that I can effect the solenoids torque and so the velocity the drum is struck by the solenoid. For now I just want to get the thing to work so I will be working at the minimum 24vdc!

I suspected that I would have to buy a ready made 240VAC/24VDC power supply as mik3 suggests so that's my starting block. One question I would like to ask regarding this: do I need to find a wallplug that provides exactly 0.79 amps? Can I use one rated at 24VDC / 1 amps or 2 amps or 3 amps? Ultimately do I have to worry about the power supply providing too many amps or do I just need to make sure that the amp rating on the power supply is at least 0.79 amps?