relay energize problem

[burningman]

I was wondering if anyone could offer suggestions as to why my relay isn't energizing? I am using the EA2 5NJ (5v relay) and testing one pole of the relay for continuity contacts. I am reading 4.6volts across the coil/w protection diode, but there is no continuity between NO and CO only between NC and CO. Essentially the relay has voltage applied to its coil but is not activating the switch to allow flow of current between NC and CO.

Could this have anything to do with the driver? I am using 2n3904 with voltage source applied to emitter, .22uf cap between base and collector and collector connected to relay negative side.

Thanks.

[burningman]

any ideas?

[biggy boy]

Can you measure your coil resistance?
It is supposed to be with in 10% of 178  ohms
Maybe it got over heated when soldering?

Glen

[burningman]

I am developing with the PicKit2 so no soldering involved at this point - the resistance is sitting at about 184ohms. Since I am also powering my breadboard with the Vdd from the PicKit2 I am now thinking it has to do with how much current I am sourcing. Just read the manual and the current consumption should not be above 25ma, whereas the EA2 5NJ requires at least 28ma.

I wonder how I would take a current measure at the relay to see how much it is drawing?

[R.G.]

All relays make a distinct click when the contacts move. Does yours click when you apply 5V across it with a pair of wires?

If you can measre 188 ohms across the relay, chances are the coil is fine. Otherwise you couldn't measure the wire resistance, which is what that is.

Measure the voltage across the relay when it is not energized, and when it is. Do you really get to 5V across the coil? If you are using a PIC, you're probably using a voltage regulator, and a regulator might be going into current overload. Just a thought.

It is always possible to get a bad relay, but it's the last thing to consider.

[burningman]

Its reading 4.7V across it. I am using the PICkit2 dev board and from reading the user guide it is saying that I shouldn't exceed 25ma - the ea2 of course requires 28ma. Would this be the culprit and could I have damaged the on-board chip or the relay?

[burningman]

just to add, the relay does not make a clicking noise

[R.G.]

Divide and conquer.

Take the relay out of whatever lashup you have it in now and place it belly up on the bench so you can get at the pins.
Connect up your ohmmeter leads to the C and NO contacts on the relay; should read open.
Now touch one wire from ground and one wire from 5V to the relay coil contacts manually. Does the meter reading change to shorted?

For this to work, the connections must be actually connected, the wires must be touching the correct terminals on the relay.

If the meter does not change, the relay is busted. This is the fundamental function of a relay - when there is enough voltage across the coil, it operates. If that is not true, it's either hooked up wrong or broken.

[burningman]

Thanks for the suggestion R.G. the reading didn't change with 5volts applied. I wonder if it has to do with a lack of current going through the coil? the PicKit2 recommends not exceeding 25ma. How would I test how much amperage the relay is eating up?
thanks.

[terminalgs]

If using 12v heater supply:  pin 9 is not used,  pin 4 and pin 5  are used.  give one 12v+ and ground the other. @12v the heater draw is 150ma.
If using 6v heater supply:  pin 4 and 5 are jumpered together and get 6v+ and pin 9 is grounded.  @ 6v the heater draw is 300ma.

9v is not enough for a 12v heater.  the current draw from the heater would kill a battery quick, so you ought to be using a transformer of some sort.  might as well be 12v instead of 9v.  better yet,  get a 120-200v transformer and give a 12ax7 high plate voltage.  everything becomes easy once you do this. 

[biggy boy]

If using 12v heater supply:  pin 9 is not used,  pin 4 and pin 5  are used.  give one 12v+ and ground the other. @12v the heater draw is 150ma.
If using 6v heater supply:  pin 4 and 5 are jumpered together and get 6v+ and pin 9 is grounded.  @ 6v the heater draw is 300ma.

9v is not enough for a 12v heater.  the current draw from the heater would kill a battery quick, so you ought to be using a transformer of some sort.  might as well be 12v instead of 9v.  better yet,  get a 120-200v transformer and give a 12ax7 high plate voltage.  everything becomes easy once you do this. 

I'm puzzled

Glen

[R.G.]

I'm puzzled

Reply to wrong thread.

Thanks for the suggestion R.G. the reading didn't change with 5volts applied.

So (assuming you have read the datasheet on the >>relay<< and are probing the correct pins) the relay is not changing state when 5V is applied.

If that is true, and you are probing the correct pins, the relay is shot. But be triply certain that you have the correct pins before making that presumption.

I wonder if it has to do with a lack of current going through the coil?

It might. If there is no current going through the coil. You posted earlier that the coil measured 184 ohms with your ohmmeter, and that is within the range of valid coil resistances for this relay, you've said. If you have 5V across a real 184 ohm resistance, the current has to be 5/184 = 27.1ma. But you can test that.

How would I test how much amperage the relay is eating up?

Timely quesstion. 
Look at your DMM. Does it have current measurement scales? The simple way is to hook up a 5V supply with the (-) to the (-) pin of the relay coil, the red/+ meter lead to the +5V (and also plugged into a different current reading hole on the meter, if needed), the black/- meter lead connected to the (+) pin of the relay coil, and the meter set to read about 27ma. You can then read it directly.

[burningman]

I placed the - probe on the negative coil contact and the + probe on the positive coil contact. I even swapped the relay out for another. The DMM isn't reading any amperage from the relay with 5v applied (grounded of course). For the reading I set my DMM to 200ma (dc) with the common plugged into the 200ma max. I'm going to try pulling together a power supply with extra amperage to spare - I think the usb available current of 100ma to the PicKit2 and its specs of not exceeding 25ma is the culprit. Any other ideas, feel free to fire them my way.
Thanks.

[pjwhite]

Could this have anything to do with the driver? I am using 2n3904 with voltage source applied to emitter, .22uf cap between base and collector and collector connected to relay negative side.

This arrangement sounds strange.  The way I would normally drive a relay with an NPN transistor in a positive power supply system is:
- transistor emitter grounded
- transistor collector connected to relay coil (-) and diode (anode)
- transistor base connected to current limiting resistor
- other side of current limiting resistor connected to logic level (0V = relay off, +5V = relay on)
- relay coil (+) and diode (cathode) connected to V+

[burningman]

Would the logic 5+volts be referencing the same voltage as V+? 

[solderman]

Would the logic 5+volts be referencing the same voltage as V+? 

Hi I'm doing the same thing as you are right now. I'm gonna use it in a multipurpose switch box. At first mine did not work but that was due to me shifting the polarity to the coil wrong even though I was "certain" that I had it right the first time.  so check that. The really is a Omniron G6H-2-100 5V its the same function as the one you use. To source the 5V I use a L7805 5V regulator. All works fine. The total current draw (regulator and relay) is 37mA.

//Solderman

[burningman]

I have tried swapping the the +5v and gnd at the coil in the past but that didn't seem to do anything either.

Can anyone tell me how I can test a 2n3904 for proper functioning?

[burningman]

Could this have anything to do with the driver? I am using 2n3904 with voltage source applied to emitter, .22uf cap between base and collector and collector connected to relay negative side.

This arrangement sounds strange.  The way I would normally drive a relay with an NPN transistor in a positive power supply system is:
- transistor emitter grounded
- transistor collector connected to relay coil (-) and diode (anode)
- transistor base connected to current limiting resistor
- other side of current limiting resistor connected to logic level (0V = relay off, +5V = relay on)
- relay coil (+) and diode (cathode) connected to V+

Your right about that. I meant to say that I am applying +5v to the base, emitter is grounded and the collector is going into the negative side of the coil.

[burningman]

SOLVED: you were also right about the applying voltage to the right end of the coil. I had initially tried doing so, but must had things hooked up incorrectly. The Relay now picks with into the NO Common position - yipee I should have realized that the pinout schematic in the datasheet was looking bottom up instead top down on the relay.

Thanks for everyone's suggestions and helpfulness.

[R.G.]

The EA datasheet has the dubious distinction of being one of the most obscure pinout diagrams I've ever see.