Let's Make Robots!

Darlington driver switching different voltages??

 hi all i've just stumbled upon the joys of robotics in the last week

so i'm a little green, I've read some darlington threads already but i didn't find an answer.

so does anyone know if the darlington ic can switch a lower voltage than the 

V+ input voltage ?

ie; if i use 12v into the ic pin 9 and i use picaxe to switch 12v motors

can i connect a 6v relay between the other out pins and a 6v supply

seperate to the ic voltage?

 

I'm refering to the picaxe manual 3 diagram.

I have 12v motors an 6v relays... what a pita. 

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sorry, that was a bit vague.

 all the info was in my head, duh!

 thanks muchly, that was what i neede to know.

I was thrown off by the above described 'internal  fly back diodes pin' #9,

 and was thinking that the 12v would be appearing through my little relay! 

 

ta folks! 

There are a number of IC darlingtons around, but in most cases you should be able to switch any voltage higher than Vcesat with any voltage higher than Vbesat, and even outside of that range it'll still work at least a little. I was a bit confused by your description, but I'm guessing you want to switch a +6V line by applying +12V to an NPN darlington input/base?

That'll work fine provided you connect an appropriate base resistor, otherwise too much current will go into the darlington.

 EDIT: Now that I look back at it I see you're talking about having the same block of darlingtons with different pairs driving different outputs, in which case the same applies and you can do more or less as you please. The only common connections in an IC NPN darlington array are (typically) the common reverse protection diodes and the common emitter; apart from those two things each darlington pair acts almost identically to a discrete darlington so you can treat them as such.

It would help if you specified which diagram in manual 3 you are refering to. What page and which IC?

Presumably you are refering to the ULN2003 on page 6? The answer is Yes. Connect pin 9 to your highest supply voltage (12V in your case). The outputs are open collector, pin 9 is for the internal flyback diodes.