DPDT common power rail relay

[clawrence]

Hi I am building an ROV for invertebrate sampling and video survey for freshwater fish research.

I am a long time lurker of your forum, but now that I am building my ROV I have a question I would like to ask. I have a three thruster design (3 x Rule 140 each 12V 2.9A) and I would like to run each thruster in both forward and reverse based upon the nice relay design I by Stephen Thone at http://www.homebuiltrovs.com/howtorelaywiringdpdt.html

But I am having trouble working out how to wire this really nice DPDT relay that I found (ie fits inside a 50mm PVC tube & can be cut to a row of 6 with a common power rail- see attached) in the same way as the diagrams by Steve, so was hoping someone could give me a bit of advice (I think the problem may be with the relay pole common link jumpers (F) & (G) , but to be honest I still can't figure out which terminal is the coil-even after reading and re-reading "Relay wiring for the electronically challenged). So I think although I am a decent biologist and am really enjoying making my ROV, I am probably in the bottom of the class when it comes to ROV electronics. Any advice would be much appreciated

Regards
Craig

[martinw]

For me it's not really apparent from the description table what does what (from a wiring perspective), but if you look at the PCB itself you can see the white sikscreen letters that seem to say a bit more.

So it's a PCB with transistors to control the relay coils and needs a 12VDC supply (+12VDC and 0VDC, two wires) to work on TB (terminal block) 1 and 2 (it doesn't look like it give polarity but I would guess it's that) if you number the TBs like an IC (integrated circuit) .....

http://en.wikipedia.org/wiki/File:Pin_n ... _Pengo.svg

...... and looking at the image of the relay on its own on the data sheet, i.e. TB 1 is top left, then going down the left hand side it goes 2, 3, 4, 5, then you move across to the right hand side, so bottom right is TB 6, then you go up the right hand side 7, 8, 9 and top right is TB 10.

http://en.wikipedia.org/wiki/File:Relay_symbols.svg

So you now have the 6 contacts of the relay (see picture above) to consider.

C1 is Common 1 (TB 3) and is C1 on Wikipedia, funnily enough.
NC (Normally Closed) is TB 4 and is B1 on the Wikipedia image.
NO (Normally Open) is TB 5 and is A1 on the Wikipedia image.

The same is true for the second set of contacts on the second part of the relay.

C2 TB 8 (C2 on Wiki)
NC TB 7 (B2 on Wiki)
NO TB 6 (A2 on Wiki)

You can also use the links on the PCB to replace wiring the relays (both NC and NO) to a particular polarity (12VDC or 0VDC), it's done on board but you can only use the 12VDC on the power supply to the PCB, which may be limited in the current in can supply through the PCB ......

So that leaves TB 9 and TB 10 on the board to control the coil of the relay via the transistor on the PCB labelled TR (then a number).

You can either turn the relay on with a positive voltage (referenced to the 12V supply) or a 0V (again referenced to the 12V supply) so you'd wire your control into either (not both) of the pins (I think ).

IMHO It's not really a very good data sheet for the novice to pick up and understand, I've been electrical engineering for about 20 years and it took me a while to work out what it was trying to tell me

One of the reasons I can generally work out what's going on from the limited information on the data sheet is I've designed a board in the past for our commercial ROV control system that has some similar features.

Mixed IO II Gradient 640X480.jpg (234.95 KiB) Viewed 1908 times

I hope this helps.

Martin