One time Switch

[sherby]

Hey Guys, I was making a small robot, and i need to have something, which once triggered by a High Signal stays open.

So I have an arduino, output a high signal to a transistor, this causes the Transistor to be in flow mode where the current flows from Collector to Emitter.But as i remove the signal, it stops the flow.
Is there a device or modification of the circuit, i can do, so that on Giving a high signal once, the current starts flowing, and after that on taking the arduino out, the current continues to flow, instead of stopping?

Thanks for any help.

[jwatte]

Just add a flip-flop. Or something like a relay with self-latching.
How do you want to turn this off, later?

[arigid]

You can use a pull up.

[newInRobotics]

Is there a device or modification of the circuit, i can do, so that on Giving a high signal once, the current starts flowing, and after that on taking the arduino out, the current continues to flow, instead of stopping?

--> http://homemadecircuitsandschematics.blogspot.co.uk/2011/12/simple-and-useful-transistor-latch.html

[paulstreats]

Latch switch is what your looking for, do a google search and im sure you'll find many example circuots and ready made devices

As a basic concept, imagine 2 transistors, the emittor of one transistor to the base of the other, then the emittor of that one to the base of the first one. All you need is to send a single signal to the basr ofthe first, trning it on, which tturns the second one on, this flows back into the basr of the first thereby latching each other on.. A capacitor would be recommended to prevwnt momentary voltage drops from keeping them going