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Canada
Asked — Edited

Look What I Got

Hello everyone!

I just got my first shipment of parts from china which included:
8x relays
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and
1x 5amp adjusting power adapter(Audiowind).
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Just waiting for some regulators, and I should be good to finish some robots!

A question:
Relay wiring?

Relay:
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How do I wire this up?

Thanks,
Tech


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#3  
does that have a transistor on the board? I don't think you should be connecting it directly to the ezb without a transistor. Also a diode is necessary on relays because when the relay closes, the voltage is reversed and pushed into the circuit.
PRO
Canada
#4  
Lol I was thinking the same thing as @DJ that board may use an LED as a flyback diode but it doesn't look like there is a driving transistor there to handle the current needed by the relay (unless it's surface mounted under the relay or on the other side of the board)
United Kingdom
#5  
I assumed these would have the switching transistor circuit built in to them but perhaps not. @Techno, post either a link to the part or the datasheet on it. Also a picture of the other side would be useful.
#6  
Good point... I never thought to ask as I have some that look very similar... They run on 5V and draw about 20ma so I am able to connect them directly to the ezb @Tech do you have the stats on the relay board?
#8  
@Tech... Just looked at the stats... You can safely drive this relay right from an ezb digital port...

Quote:


EBay Description:

5V 1-Channel Relay interface board, and each one needs 15-20mA Driver Current
United Kingdom
#9  
That datasheet is for just the relay which is on the board not the board itself.

It looks like, as Richard said, you can drive it direct from the EZ-B (as per my first reply) however check to make sure it does have the driving transistor and diode otherwise there is a risk of damaging the board, the EZ-B and the battery.

If in doubt, add a driver circuit. This would be the TIP122 circuit with the optional diode.

Or if you are feeling brave and want to risk the warranty on the EZ-B you could just try it and see what happens however I don't recommend that option personally:)
#10  
If you really want to be sure you could always test it with a multimeter first to see how much current (at 5V) the relay uses to close...
United Kingdom
#11  
@Richard, with no diode there is a chance of back feed from inductive loads. You don't want back feed into a LiPo battery... You don't want back feed anywhere to be honest:)
#12  
Any which way, I have a couple of transistors(don't ask where I got them from)
that are 2n2222 transistors.
2n2222

Will these work?
*Added picture of pin layout*

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#13  
@Rich, I guess I didn't even realize it or even thought about it as have only been using niMh batteries in most of my projects... Still, good to know... Thanks...
#14  
Will those transistors I mentioned in my last post work?
#15  
I know I've arrived late in the game but I purchased several of the 5 volt relays for use with one of the Roomba projects (not completed yet) but I did post some info about them a few months back. One key reason for my selection was that the relay boards are optically isolated from the EZB or any microcontroller for that matter. Also on ebay: http://www.ebay.com/itm/5V-1-Channel-Relay-Module-H-L-Level-Triger-with-Optocoupler-for-Arduino-Raspberr-/221407959915?pt=LH_DefaultDomain_0&hash=item338cf15b6b


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PRO
Canada
#16  
@TechnoPro Just wanted to chime in that a 2N2222 is perfect for this application, and a 1N4148 or 1N4001 should work for a fly back diode.
#17  
Thanks Jere! ...How would I wire it up...?

Robotdoc, are you saying that my relay is fine by itself? Or is that just for what you have linked?
#18  
Technopro - No the link is for the optical isolated relay. The ones you have evidently are not power isolated.
#19  
Ok, well if I happen to buy more relays I'll go with those! Thanks Doc.
#20  
Jeremie, are you sure of the 1n4001's? I read they are forward voltage vf 1.1v.
PRO
Canada
#21  
Hi TechnoPro,

Most of the examples online use a 1N4001 or it's higher voltage cousin the 1N4007. Forward voltage doesn't really matter in this case as the diode is just being used in a flyback configuration which means that it is dissipating the energy left in the coil once the transistor stops conducting, efficient forward voltage doesn't really matter in this case.

Here's a schematic for interfacing directly to a relay from the ez-b:

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While I am pretty sure that 3.3VDC will work with a 5V relay, if it doesn't then use 5V instead of 3.3V and increase the resistor to a 2.2kohm
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