Arduino to relay drive circuit.

Using Arduino General Electronics
1

Folks,

It has been a long time for me.

I can "bash up" a transistor circuit with flyback diodes easily enough.

But my project required 5 relays to be operated by five different pins.

Is there anything out there to make the job easier nowadays?

Worst comes to worst it is 5 x NPN trannies, 10 resistors and 5 diodes. I'm guessing that would probably be the easiest.

Yeah, well, ok then the 5 relays.

2

ULN2003 or ULN2803

3

Absolutely! or maybe a TPIC6B595??? and save the diodes ( there are 'body' diodes on each Fet Drain Lead... Just a thought...

Doc

4

I can easily get the ULN2003 so I think that will be the go.

Looking at it, I'm taking it that if I send +5 on the input, the outputs go low, or to 0V.

Also, I'm guessing there is no way to make it that I put in 0V and the outputs go high. There is no + supply to the chip that I can see on the data sheet.

5

No the transistors are wired "Open Collector" I mentioned the shift register as a means to save pins with the same or very similar drive capabilities and can be done with 3 wires for 8 outputs cascadable too.

Doc

6

Doc,

Sorry for the confusion.

I know I usually am "pin worried" about use of pins.

Alas where I am (OZ) the availability is not as good as it maybe could be.

That TPIC6B595 looks really nice, but I can't find one easily here.
Sure it is accademic, as they don't come from here anyway, and are made O/S.
Just the logistics of getting them by post can (sometimes) be more trouble than it is worth.

Tomorrow I am off to the local shop to buy the ULN2003 and a socket, a handful of relays and I shall start building the hardware side of things.

But I think that belongs more in my "potted plants" thread than here.

Thanks though.

7

Don't use a socket for the 2803's If you are driving heavy loads... the heat-sinking is the output leads. For light loads (50 ma or less like Small relays) a socket and breadboard is ok but remember the 2803 is a power device and can get quite hot mounted and soldered to a PCB. As to the TPIC... devices they are about $2.00 ea on Ebay... I buy a LOT there... I just schedule my projects around the delivery time and I LOVE to get all those small bags of goodies, I can buy twice as much stuff for the same money.

Doc

8

TPIC6B595's are cheaper at regular distributor
$1.53 http://www.mouser.com/ProductDetail/Texas-Instruments/TPIC6B595N/?qs=JHHQeKcAU3CAIuVjF6zqmiTAjbztk8hLKgHqiPVXvd8%3D
$1.66 TPIC6B595N Power Logic 8-bit Shift Register 50V 150mA 5Ohm Cascadable - dipmicro electronics
$1.74 http://www.digikey.com/product-detail/en/TPIC6B595N/296-1956-5-ND/277601

$0.82 https://avnetexpress.avnet.com/store/em/EMController/Counter-Shift-Register/Texas-Instruments/TPIC6B595N/_/R-1750249/A-1750249/An-0?action=part&catalogId=500201&langId=-1&storeId=500201&listIndex=-1&page=1&rank=3

e-bay not always the deal one might think.

9

Thank you for the tip on the Avnet price/link heads up. Ebay sellers overprice anything that remotely can have Arduino attached in any way to it. I do however by shopping get some deals here and there, Here and there. I bought 100 TO263? (smaller than TO-220 SMT devices) 5 A P ch mostets for 7.50 today and a US shipper too postage was $1.20... Thought that was a great deal and I will have them on Saturday.

Doc

10

Something comparable to this?

100, $32.45

And you got 100 P-channel MOSFETs for $7.50 plus $1.20 shipping? Nice find.