# How do I increase the drive current from the arduino digital pins?

I'm new to the Arduino (using the Leonardo). I am working with a heatplate that gets hot when you apply power to it.

When I use the 5V Vcc pin it works fine. But when I use the digital pins I don't get enough current.

Is there any easy way to increase the amps you can get from the digital pins?

Would somebody have a simple driver circuit?

Thanks for the answer. This is my setup. I don't know exactly how much current the plate needs to get a high temperature fast, but i'm guessing in the range of 0,5 A - 1 A.

So basically, I need to use the transistor as a switch and then use another power supply for the heatplate-thingy ?

EDIT This is a picture of how I planned to do the setup. Feedback is very much appreciated.

• The picture doesn't show the plate's specs, so no help here. I don't know the current capacity of the Arduino board. 1A may be a little to much for it, but this is a guess. The picture also shows you are powering it via the USB port, which may limit your power availability. If your power source and power circuits can't handle the plate's power requirements, the you'll need another power supply indeed (note, however, the common GND point). Otherwise, you can power both the load and the MCU board with one unit. It's all a matter of balancing what the loads needs and what the PSU can supply. – ricardomenzer Dec 2 '15 at 14:00
• The picture shows my initial setup. I have been testing a 12V 500mA power supply connected directly to the plate and it works fine. So what I want is to use the digital pin on the arduino to control when to power the plate and when not to using a transistor. – Alexander Ibsen Dec 2 '15 at 14:24
• Then the circuit in my answer is what you should look for, using separate PSU for the arduino and the heatplate. – ricardomenzer Dec 2 '15 at 16:51
• That "heatplate-thingy" looks like a Peltier Module, i.e. solid-state heat pump, so one side gets warmer other side cooler. Looks like about 40mm x 40mm, could be a 75Watt? 15A? module... any clue where you got this part? – MarkU Dec 2 '15 at 21:40
• Got it from a guy at my University because I need to create a prototype that uses high temperature as feedback to the user. I think you are right, it is a Peltier Module. I think I found a transistor I can use, a TIP120. But I am not really sure. I will post a picture of how I plan to do the setup. – Alexander Ibsen Dec 3 '15 at 15:15

You will have to use a transistor to drive the heatplate.

Something similar to this:

simulate this circuit – Schematic created using CircuitLab

Note that this is a simplified general circuit. Without knowing the specs of the load you are trying to drive, we can't specify which components to use.

EDIT: Based on your info of the voltage of the load's supply and that you already have a TIP120 to switch its power, consider this circuit that I found in this site. As @Matt pointed, a flyback diode will not hurt anybody.

simulate this circuit

• Needs a gate pull down. Ideally add a series resistor to the gate. A flyback diode never hurt a MOSFET circuit either. – Matt Young Dec 2 '15 at 20:31
• Yes, like I said, this is an overall idea of circuit. It needs some tweaking. Is the pull down resistor needed? Haven't the Arduino has strong drivers on its outputs? – ricardomenzer Dec 3 '15 at 12:28
• I don't know what a pull down resistor is to be honest. – Alexander Ibsen Dec 3 '15 at 15:17
• @AlexanderIbsen See this answer. A pull down is similar, but pulls the input to the 0V. – ricardomenzer Dec 3 '15 at 16:36