Driving SPDT relay using PIC18F2580

[Gaara]

Hi all,

@Mike Walne:
Apologies. This was an error on my part WRT the post. My relay is the G5Q-1 and indeed it is an SPDT based relay. Thanks for clarifying which of the pins is the COMMON.

@Ttelmah and @gpsmikey:
My PSU details are as follows:
Input: 100v - 200v - 50 - 60 Hz - 0.2A.
Output: 6v - 150mA.

The actual output constantly reads 6.4v hence looking at the dropout voltage of 1.3v an output of 5v is obtained which is what I read from the Vout pin of the regulator.

@avro698:
I've connected my wiper, common or pole pin i.e. pin 2 to ground and the LED load doesn't toggle.

@Everyone:
As opposed to using the ULN2803 with regards to driving the relays I would like to utilise a combination of an NPN transistor and a diode to drive the relay, in similar fashion as seen on page 10 here http://www.apogeekits.com/PDF_Files/illustrated_assembly_manual_k8090.pdf

Having read more on this method of driving the relays using a PIC is this method any better than using the ULN2803?

With regards to ironing out the PSU as a reason as to why the relay might not be working I applied, Ttelmah's advice below:

Which is why I prefer to separate logic and relay supplies.

Remember this can (to a limited extent), be as simple as having one 5v rail, feeding the relays, and then having a resistor/capacitor filter feeding the logic off this.

[ezflyr]

Gaara,

Some time ago you said this:

[gpsmikey]

I have had a copy of the audio track of that for years, but not the video! Thanks for that link (and yes, it does apply). Too often (and here is an example) if it doesn't work, they re-arrange the deck chairs on the Titanic and try again instead of learning to troubleshoot the problem. That is a basic skill you have to develop if you expect to survive anywhere in the industry (or life for that matter). Start with simple test code that toggles or whatever something in the hardware to make sure that part works. Move on to the next part. Once you have verified each part works, then work on integrating the pieces together.

mikey
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mikey
-- you can't have too many gadgets or too much disk space !
old engineering saying: 1+1 = 3 for sufficiently large values of 1 or small values of 3

[Ttelmah]

Still no details of whether the supply is regulated or not.

The transistor gives the same result as the ULN. Remember you need the diode, transistor, & minimum two resistors for the circuit. No advantage at all.

The serious difference, with the manual connection, is that if the supply droops when the relay switches, the PIC will almost certainly reset, while the manual connection will stay solidly high. I'm strongly suspicious your 5v rail is _not_ maintaining a good 5v, when the relay tries to switch. Even with the LDO regulator, you are below the 'dropout' voltage for the regulator. An oscilloscope on the supply rail when the relay switches, might well show your whole problem.

[Mike Walne]

It's time for a review of where you're at.

Starting from RC1 tell us, clearly and precisely, which nodes in the circuit path to the relay contacts are toggling and which are not.

Mike

[afyon]

@Gaara, I really don’t understand, how can everything so simple just won’t work? There has to some reason for that. Please check if there are any grounding issues in your circuit. These are the most common cause for such issues and generally with grounding issues, nothing seems to work properly. Since your regulator isn’t giving a proper output voltage, there can’t be much more that can go wrong with the circuit.
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prototype pcb assembly