modify a remote controlled machine

Hi, I'm italian, sorry for my English, i'm modifying a remote controlled car, i only want to turn on the engine, it has 2 cables, if I put one on 5V and another on the ground it goes ahead and vice versa. But if I put the cables in the digital pin and I try to put HIGH on a pin and LOW on the other it doesn't turn on. Do I have to use a relay? or can I resolve without it?

Igor16: But if I put the cables in the digital pin and I try to put HIGH on a pin and LOW on the other it doesn't turn on. Do I have to use a relay? or can I resolve without it?

Upload an schematic of your connections to understand properly. And you don't need a relay but a transistor, but to help you you have to give more details (which kind of motor, dc or stepper, power supply, etc..)

thanks, it’s a dc motor, like the motor on chinese cars, i give it 5v, so what kind of transistor do i use?
I attached the image which I think it’s the right method to make the circuit, but i don’t know how to invert the 5V and the gnd

Igor16:
thanks, it’s a dc motor, like the motor on chinese cars, i give it 5v, so what kind of transistor do i use?
I attached the image which I think it’s the right method to make the circuit, but i don’t know how to invert the 5V and the gnd

Then you need an H-bridge, its an array of transistors that can drive a dc motor forward or backward. Look for h-bridge arduino on google there are tons of examples.

if i want to do it on breadboard with multiple transistors which transistors i have to use? i see on ebay 2n2222 or 2n3906, which of these one do i have to choose?

The first problem is that you indicate the intention to power the motor(s) from the Arduino power terminals. This is not going to work. The motors will require far more current than the Arduino can provide and you could easily damage things trying to do so.

You need a separate power supply - possibly a battery such as four alkaline AA cells in a holder.

You need a multimeter. If you do not have one, stop the project right now and go buy one - a $US5 one with a 10 Amp range will be fine.

Use it to measure the current drawn by the motor when connected to the 6V battery while you hold the motor shaft so it cannot turn. This is the "stall" current and you must choose your transistors to be rated for more than that current.

If you have these details sorted out, we can then discuss the circuit.

Igor16: if i want to do it on breadboard with multiple transistors which transistors i have to use? i see on ebay 2n2222 or 2n3906, which of these one do i have to choose?

You better buy a ready-to-use H-bridge (SN754410)

http://www.ebay.com/itm/1PCS-SN754410NE-IC-HALF-H-DRVR-QUAD-16-DIP-NEW-GOOD-QUALITY-/201191353704?pt=LH_DefaultDomain_0&hash=item2ed7f06d68

can i use my driver ULN2003 for stepper motor? if i can use how does i have to make the circuit? thanks

i only want to turn on the engine, it has 2 cables, if I put one on 5V and another on the ground it goes ahead and vice versa.

An H-bridge allows you to connect +5/GND to motor terminals 1 and 2 to spin the motor one direction; and then connect Gnd/+5 to motor terminals 1 and 2 to spin the other direction. A ULN2003 can only do one direction.

thanks, with SN754410NE can i control 2 different motors at the same time?

So, what was the stall current when you measured it?

i can't measure it

Igor16: i can't measure it

Looks like nothing more to say then.

i ordered the h bridge, i don't have a multimeter but maybe i could buy it, but i think if it works without the h bridge it works better with it, isn't it?

Igor16: i ordered the h bridge, i don't have a multimeter but maybe i could buy it, but i think if it works without the h bridge it works better with it, isn't it?

What do you mean by saying "work without the h bridge"? Work what?

the 2 motors, i attached them to the 5v and GND of Arduino, so i think they also work with h bridge