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Topic: What type of transistor do I need? (Read 493 times) previous topic - next topic

drsdrs

I currently am working on a project that powers a 7.5v motor that can be toggled on and off with a remote.  I have everything hooked up the way I need it but the transistors that I have end up breaking when more than 5v is passed through them.  Can someone tell me what specific type of transistor I need and possibly a link to where I can buy one?

polymorph

How do you know it is the voltage and not the current? A motor's starting current is equal to its stall current, which is generally quite high because when it is not moving, it is just some wire.

A schematic and part numbers would be helpful.

Are you only turning this on and off, or will you be using PWM as speed control? Do you require a high side driver, or is low side driver fine? What is the motor stall current? If you bought it recently, can you provide a link to the website page?
Steve Greenfield AE7HD
Drawing Schematics: tinyurl.com/23mo9pf - tinyurl.com/o97ysyx - https://tinyurl.com/Technote8
Multitasking: forum.arduino.cc/index.php?topic=223286.0
gammon.com.au/blink - gammon.com.au/serial - gammon.com.au/interrupts

Grumpy_Mike

Quote
end up breaking when more than 5v is passed through them.
You do not "pass through a voltage", only a current.
There isn't a transistor you can buy that will be destroyed with 5V across it.
Now current is another matter, too much of that and you will melt a transistor.

So how much current does your motor take? The transistor needs to be rated to take at least 20% more than that.

drsdrs



No Load Current:190mA(max.250mA)

http://www.dagurobot.com/goods.php?id=158

polymorph

We don't care about no-load current.

What is the current when you jam the motor and keep it from turning?
Steve Greenfield AE7HD
Drawing Schematics: tinyurl.com/23mo9pf - tinyurl.com/o97ysyx - https://tinyurl.com/Technote8
Multitasking: forum.arduino.cc/index.php?topic=223286.0
gammon.com.au/blink - gammon.com.au/serial - gammon.com.au/interrupts

polymorph

Schematic? Which transistor? How are you driving it?
Steve Greenfield AE7HD
Drawing Schematics: tinyurl.com/23mo9pf - tinyurl.com/o97ysyx - https://tinyurl.com/Technote8
Multitasking: forum.arduino.cc/index.php?topic=223286.0
gammon.com.au/blink - gammon.com.au/serial - gammon.com.au/interrupts

polymorph

#6
Jan 30, 2015, 12:10 am Last Edit: Jan 30, 2015, 12:11 am by polymorph
Stall current, 1A.

http://www.crcibernetica.com/gear-motor-dg01d-2-motors/

It is rated at a max voltage of 6V, why are you using 7.5V? It will take even more current at 7.5V and may burn up.
Steve Greenfield AE7HD
Drawing Schematics: tinyurl.com/23mo9pf - tinyurl.com/o97ysyx - https://tinyurl.com/Technote8
Multitasking: forum.arduino.cc/index.php?topic=223286.0
gammon.com.au/blink - gammon.com.au/serial - gammon.com.au/interrupts

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