Transistor Arrays

Forum 2005-2010 (read only) Hardware Interfacing
1

Hi,

I want to run a series of motors (small vibration motors that draw around 80 mA current) from the digital output pins of an Arduino BT (or maybe an XBee series1 module). Since these motors draw more current than the Arduino/XBee support, I plan to power the motors independently (with a battery pack), and use a transistor as the switching device (with the output from the Arduino connected to the base, etc.).

There are 8 such pins and I dont want to connect 8 individual transistors, because that makes the circuit messy. I know there are transistor arrays availbale (multiple transistors on the same chip), but I dont know which ones to use.

Any recommendations on which transistor arrays I should use for my application?

regards,
A

2

ULN2803

3

Hi
I noticed your brief post as I was flicking through, so maybe you could help. I'm trying to interface my Mega board with a Power Distribution Unit to give me individual control over the 10 relays on the unit. I went for a couple of ULN2803A arrays, but I can't get anything to happen. The switching works fine with a single transister, but for space saving and minimalising work load I wanted to go for an array. The relays are 24V, coils are 1100 ohms, so in my limited knowledge and experience, I figured that the ULN2803 arrays would be perfect. Wiring is as per the Data Sheet, but no joy. Can anyone shed any light on this ?

Cheers
Andy

4

Wiring is as per the Data Sheet, but no joy. Can anyone shed any light on this ?

Folks might be able to help if you post more information.

Would you post a schematic (hand drawn and photographed would be okay)?
When you say wiring as per data sheet, do you mean the ULN2803 data sheet, or the Power Distribution Unit or relay?
Would you post a link to the data sheet fpr the Power Distribution Unit. (Might be helpful if you post a photo of the wiring too.)

Have you done a quick test using a LED and resistor in place of a relay driven by a ULN2803? Does that work?

GB

5

Did you remember to connect Arduino ground to the ULN2803 ground ?

6

Hi Guys
Sorry for not getting back to you sooner, I was trying to upload photos of my board. But failed! That doesn't bode well for the rest of the project!!

Anyway, problem solved. My 24v Common wire wasn't! Fed in the correct 24v input and all darlington pairs now working as advertised.

Thanks for your comments anyway.