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darlington drivers

Hey all.

Calculon has a question about the uln2803 darlington driver. He has a datasheet that says "the darlington pairs may be connected in paralell for more current-carrying capacity."   Calculon wonders how this is done?

Would that be pair of darlington pairs? And if he wanted more current capacity than that, what transistors would he use to make his own d-pair?

Calculon thanks you.

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does anyone know if the 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. 

The common, pin 10, of the ULN2803 must be connected to the supply voltage, either 6 volts or 12 volts. It cannot be connected to both.

Add another ULN2803 for 6 volt use, or add some transistors to run either one device or another. 

 edit : in another post, others think it will work. Having not tried it myself, perhaps it might. I'd expect the 6 volt relay coils to see overvoltage during switching though.

You will need a heatsink and it can drop a few volts being a BJT.

Otherwise for switching use a Nch Fet such as a MTP3055V which can handle up to 12A. No heatsink is required for 1 or 2 amp. I used these to drive SplatBots water pumps.

http://www.fairchildsemi.com/ds/MT/MTP3055V.pdf

I thought it was his inner monologue expressing itself....
lmao... whatever makes you happy man... :)

Calculon is embarrased.

Thx MintVlt

minty is glad to point calculon in the right direction
picaxe manual 3 page 6. i wont post a link because i use safari ;)