# Using Transformers to run high voltage

Hello All,

I am looking to step up the 5V from the Uno that I'm using, and I need the voltage on the other end to be around 110 V. I sourced the transformer out of a wall wart, and I'm thinking that it will work well, provided that I rectify the whole AC/DC situation, but whenever I plug wires into the leads of the transformer the board shuts off. I tried using a pin and a digital write high, but the pins all shut off when I plugged the wires in, too. I don't quite understand why the board just shuts off, and any ideas on how to fix the problem would be greatly appreciated.

If you pass dc through a transformer winding, it will appear as a short circuit.

We need a diagram.

Are you pulsing the arduino output? Put DC on a transformer and all you see is a short.

You do know that you will get a lot less current out of the other end of the tranformer, right? If the arduino can source about 10 mA, you can expect only about .01 * 5/110 out the other end. In other words, you get no magical increase in the power available.

Here’s a schematic, and yes, I know there will be a current drop. I will try to pulse the DC and see if that fixes it

Assuming you haven't already burnt out the arduino.

KeithRB: Assuming you haven't already burnt out the arduino.

The back emf on the transformer winding may be enough to finish it off :)

It still works and runs my program with just wires, so the board is fine. I just need to output a higher voltage, and its not like I'm sending the high voltage back to the board, I'm trying to step up the voltage in the wires of the output.

I have a DC/DC voltage booster that I could probably use, would that be a better idea?

"A little knowledge is a dangerous thing..."

Your schematic drawing skills exceed the average Newbie but you know not what you do.. (you lack the most very basic understanding of AC & DC)

As already mentioned the transformer presents a short circuit. If you want 110V dc you need a switchmode power supply. You would be better off with a DC-TO-DC boost converter but 5V to 110V is a 22:1 step up ratio and not easy to find. I built a 12V to 220V dc boost ps using two ATtiny85s . It used two switching frequencies (150 hz & 150 kHz) but I am not inclined to give the schematic to someone who doesn't understand basic electronics.

What is E.D.D. ? (Here in California it's the Employment Development Department: where you wind up when you get laid off)

What is E.D.D. ? (Here in California it's the Employment Development Department: where you wind up when you get laid off)

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It stands for Engineering Design and Development, and it is the capstone course in the Project Lead the Way cirriculum for engineering. (I'm a high schooler, just btw), and I get that using a transformer shorts the circuit, believe me, I do, but, as you mentioned, a 22:1 step up is not common. I did see on the Arduino Playground a board that created a step up, and that would probably work, so I suppose I'll try that next.

Thanks for the, um, complement (???) on my schematic skills, and thanks for your advice.

Do a search for transformer operation, or some such, to gain an understanding of transformer action. In short, a transformer requires a varing magnetic field between the primary and secondary windings. Now there are many other factors in transformer design that are way beyond the scope of this thread, but it is sufficent to say that you MUST have a varing field to make a transformer work. With AC line applied the field varies at the rate of the AC line voltage (60 Hz in USA and 50 Hz in the UK, sorry to others as these are the only ones I know for sure) which is the most common transformer action. Switch mode power supplies work the same except the frequency is much higher which allows the transformers and capacitors to be much smaller and lighter thereby saving space, weight and cost all while increasing effency. A person can simulate, to a point, the action of AC voltage by pulsing a DC voltage at a simular rate into a transformer, but the inrush current will be quite high while the transformer core is magnatizing and the reverse EMP will really snap when you turn off the pulse. This is how old automotive radios with tubes (valves) worked to get the required high voltage from a 6 or 12 volt DC automotive electrical system using a part called a vibrator (buzzing switch). Just a brief explination that barely brushes the tip of transformer theory.....

Good Luck, R

Hi, why do you need to transform 5V to 110V? Simple question. Tom...... :) Can you give us a proper circuit diagram, showing all connections to the arduino and transformer?

I read the words "Medical Electrode Wires" on that diagram.

My advice - choose another project! Now! :astonished:

He's probably trying to get back a dorm roommate who took his favorite shirt. :D