Interfacing Velleman Kit K8056

Hi,
I would like to drive the inputs of the Velleman relay board (K8056). The schema of the card is available here: http://vesta.homelinux.net/mediawikidir/e/eb/K8056_sch.jpg

Do I have to use a DS2405 (and a 2N3904), or can I directly use the digital entry of the Arduino (i would bet on the 1st proposal)

If someone can help me with the wiring, that would be great! :wink:

ps: using this relay card, do you think I can drive small water pump (for a fish tank)?
ps: I will use it on a 220V power source.... ::slight_smile:

Thanks!

  1. Yes, you can use the Arduino's digital outputs to control it; based on the schematic, using terminals OUT1-OUT8 (which connect to NPN driver transistors). I would personally throw a buffer IC in between, but then again I am paranoid.

  2. Also - you can control it via RS-232; so in theory you could set up a MAX232 device on a couple of I/O pins and go that route.

  3. Yes, these relays should be able to control a small pump; their contact current rating of 5A/230VAC is more than plenty, I would think.

  4. Finally, you are spending waaay too much money for something like that; in another thread I noted how you could build a similar relay-controller for well under $50.00 (with 20 outputs - you could probably do 8 for under $25.00). If you went with using opto-isolators driving high current triacs, you could probably do it for under $10.00 (provided you were only driving AC loads, of course).

Spend your money how you like though; I just know that Velleman kits, while nice, are pretty pricey for what you get (and what you could build yourself).

(i would bet on the 1st proposal)

You would lose :sunglasses:

There should be no problem at all with driving those transistors directly from Arduino pins.

If you want to save I/O pins, you could use a shift register or port expander, but you don't need to.

Hi,
Thanks for the answer. I still have a question. What is a "buffer IC". I am not sure of what it means.
Thanks

OK, my project is progressing well and I am able to use the shift register to put LEDs ON/OFF to simulate the relay cards I am waiting for.
I finally changed my mind and went for the Futurelec relay boards (4 i/o AC and 4 i/o DC), so 8 i/o total, that I can manage with my shift-register (DC Opto-Isolated Output Board and 4 Channel Opto-Isolated Relay Board) :sunglasses:

What kind of electronic components should I put to act as a buffer IC between my shift-register pins and the screws of my relay boards ? Is a 2n2222A a good choice (http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=497-2598-ND)? :-?

I still have a question. What is a "buffer IC". I am not sure of what it means.

The simple answer is it is simply an IC that sits between a set of digital inputs and outputs and acts as a current booster and protective layer between those - so if something goes wrong, the buffer gets fried.

In a way (and probably how they are implemented, but I am not sure) they are simply driver transistors packaged in an IC (think of it like a darlington driver IC, but without the secondary transistors).

The classic version is the 7404 hex inverter IC; the only problem with it is that it inverts the signal (basically acting as a NOT gate). There are versions which don't do this as well.

It probably doesn't matter nowadays with microcontrollers being so cheap, but I come from a period where an 8-bit CPU ran $20-50.00 in low quantities and you didn't want to blow them by hanging just any old transistor off your data bus.

Those were the days when you could look at your i/o port wrong and it would blow...

:smiley:

So something like the M74HC367 http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=497-7367-5-ND?
If yes, can you confirm i can use it for only 6 of my 8 shift register outputs?, so I will have to buy 2 of them?
Thanks

Yes - that should work OK; and yes, you would have to buy two (might as well buy a tube worth if you can afford it, you'll probably need some more in the future if this isn't going to be your only project).

Also - remember to tie G1 and G2 to ground (so the signals will pass thru to the outputs - read the datasheet) - you could also control G1 and G2 with the Arduino (if you needed that capability for some reason).

:slight_smile:

Thanks again. Since you are reading in my mind, do you know by which way I could use only 1 arduino pin to control both the shift-out register OE pin and the G1 and G2 pins of the IC buffer at init time. Since OE must be low and the other be HIGH before using them, I do not see any easy solution, do you?

Thanks

up? nobody?