Timer board

JohnW2 said:

You're not alone ... that very fundamental problem had not occurred to me (probably because, had it not been suggested here, I would probably not have dreamed of putting a diode across the switch/relay contacts!), either (and it seems that the penny didn't drop for SUNRAY, either!).

In any event, that's a pretty good reason for putting the diode in the 'correct' place (across the coil) .

Kind Regards, John

Click to expand...

Oh the penny dropped OK, I thought it too obvious to mention...

Hence the

SUNRAY said:

Oh the penny dropped OK, I thought it too obvious to mention... Hence the

Click to expand...

I suppose I have to take your word for that As for myself, I freely admit that it had not occurred to me - (otherwise I would obviously have mentioned it as a reason for not putting the diode across the switch/relay contacts!!) although that never would have been a problem for me, because I would never have dreamed of putting the diode in the 'incorrect' place, anyway!

Kind Regards, John

A contact suppressor ( resistor and capacitor in series ) across the relay contacts would help to protect the contacts.

Dare I mention bifurcated contacts..... there I said it

bernardgreen said:

A contact suppressor ( resistor and capacitor in series ) across the relay contacts would help to protect the contacts.

Dare I mention bifurcated contacts..... there I said it

Click to expand...

You may.



But...




What does that have to do with back EMF?

SUNRAY said:

What does that have to do with back EMF?

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From my day's in telephones. One contact does the dirty work and gets worn from the back EMF from relays and transformers in speech bridges while the other one stays clean and makes a good clean connections without creating any noise to interfere with the speech.

bernardgreen said:

From my day's in telephones. One contact does the dirty work and gets worn from the back EMF from relays and transformers in speech bridges while the other one stays clean and makes a good clean connections without creating any noise to interfere with the speech.

Click to expand...

How does each contact know whether it is the 'one that does the dirty work' or 'the one which stays clean'?

Kind Regards, John

@JohnW2, or anyone else educate me please, regarding your earlier comment a few questions

Sparkymarka earlier suggested an IN4001 diode as do google, but you both implied IN4004 was fine and I got the impression my IN4004 would be fine but the PIV of 400V was a bit over the top, can you elaborate on that please.

In case i come across this situation again, I have some more IN4004 diodes , but should i stock up on IN4001.
We sometimes only have to to check the mains power supply to maglocks, but if we can solve the other non mains issues, like this case thats a bonus.

Therefore Is there a diode size that would likely cover the range from small to medium locks both 12V and 24V, I do not know off hand current ratings but can likely find out.
But seems they all are about 500ma. or less

Also it does appear that most locks have something built in, therefore is it a problem if a Diode is still added, I assume its not a problem.

Anyway I fitted it within the maglock casing and all appears fine, apparently over 4 years and over 6 people have looked at this lock and not solved the issue, so the Manager was well happy.

A bit of background on the job, its a pub external yard gate that leads to the beer garden, but the buttons in the pub, therefore to get from the button to the gate was a 2 man job, now he can hit the button and walk to the gate within the delay and still get in.

One final question though, I fitted it by using the indicator Marking on the casing, I therefore assume it is the right way round and feel that if it was the wrong way round, i would be right to think it would have Dead shorted the power supply.

It amazes me how something so small can do what it does, so therefore a final query, does the diode get hot and is its lifespan limited.

Thanks for all your help EVERYONE, i have learnt more here, as usual than I ever did on my C+G Electronic servicing course about 10 years ago
As usual things are easy when you know, pre maglock days we used to change a lot of the Solenoid deadlocks and my friend at RS used to always bang on about there Emf and Diodes, I should have paid more attention.

If it was the wrong way …it wouldn’t work and probably blown the fuse in the psu …depending on psu type …

333rocky333 said:

@JohnW2, or anyone else educate me please, regarding your earlier comment a few questions

Sparkymarka earlier suggested an IN4001 diode as do google, but you both implied IN4004 was fine and I got the impression my IN4004 would be fine but the PIV of 400V was a bit over the top, can you elaborate on that please.

In case i come across this situation again, I have some more IN4004 diodes , but should i stock up on IN4001.

Click to expand...

If you are stocking up get 1N4007 which has the highest PIV and can be used anywhere a 1N4001 or 1N4004 is used.

333rocky333 said:

@JohnW2, or anyone else educate me please, regarding your earlier comment a few questions .... Sparkymarka earlier suggested an IN4001 diode as do google, but you both implied IN4004 was fine and I got the impression my IN4004 would be fine but the PIV of 400V was a bit over the top, can you elaborate on that please. .... In case i come across this situation again, I have some more IN4004 diodes , but should i stock up on IN4001. .... We sometimes only have to to check the mains power supply to maglocks, but if we can solve the other non mains issues, like this case thats a bonus. .... Therefore Is there a diode size that would likely cover the range from small to medium locks both 12V and 24V, I do not know off hand current ratings but can likely find out. .... But seems they all are about 500ma. or less...

Click to expand...

The entire IN400x range have essentially identical characteristics other than PIV, all the way from IN4001 (PIV=50V) up to IN4007 (PIV=1000V). It therefore does not make a blind bit of difference which one you use in any application, provided only that the PIV is at least high enough. In other words, a 1000V IN4007 would be just as suitable for a 12v/24V application as would be a 50V IN4001.

It therefore probably makes sense to 'stock up' on IN4004s, since they are then suitable for 'mains' (230V) applications as well as ELV ones.

Bear in mind, though, that all the diodes in this range have a maximum current rating of 1A, so you might want something beefier for some high current ELV applications.

333rocky333 said:

Also it does appear that most locks have something built in, therefore is it a problem if a Diode is still added, I assume its not a problem.

Click to expand...

As you say, no problem.

333rocky333 said:

One final question though, I fitted it by using the indicator Marking on the casing, I therefore assume it is the right way round and feel that if it was the wrong way round, i would be right to think it would have Dead shorted the power supply.

Click to expand...

As you say, and as sparkymarka has confirmed, that would 'short' the PSU. The diode would almost certainly die and, if some fuse/whatever did not protect the PSU, that might be in peril as well.

333rocky333 said:

It amazes me how something so small can do what it does, so therefore a final query, does the diode get hot and is its lifespan limited.

Click to expand...

It would only get hot if a current approaching its maximum rating (1A) flowed for an appreciable time, and that's certainly not going to happen in your application - in which a (probably small) current will only flow through it for a very short time when the maglock's solenoid in de-energised.

333rocky333 said:

Thanks for all your help EVERYONE, i have learnt more here, as usual than I ever did on my C+G Electronic servicing course about 10 years ago

Click to expand...

On behalf of 'everyone', you're welcome.

Kind Regards, John

winston1 said:

If you are stocking up get 1N4007 which has the highest PIV and can be used anywhere a 1N4001 or 1N4004 is used.

Click to expand...

Usefull post Winston
I did see that one mentioned a lot, so did consider that, is it the same physical size as my 1N4004 ones, I still have a few left, so I may as well get the 1N4007, not that I need them and as you and others imply, they may be of use one day

333rocky333 said:

I did see that one mentioned a lot, so did consider that, is it the same physical size as my 1N4004 ones, I still have a few left, so I may as well get the 1N4007, not that I need them and as you and others imply, they may be of use one day

Click to expand...

Yes, they are all exactly the same size.

I think you will find that, presumably since they are easily the most popular, IN4004s are usually a far bit cheaper than the others. Whilst it's obviously possible that you might need a 1000V PIV diode "one day", the 400V PIV of a IN4004 is adequate (and 'usual') for 230V RMS applications, so I think it only very rarely that you would need anything with a higher PIV - which is why In4004s are, I think, what most of us (certainly myself) keep significant stocks of.

Kind Regards, John

https://cpc.farnell.com/search?st=1n400
seems to defy pricing logic, and as usual are *much* cheaper than Farnell who own CPC.
1N4007s are 3p each for 10.

Ok thanks @JohnW2 to be fair I have enough 4004 for my needs so im gonna get a few 4007 as there less than a couple a quid, scanning the net 4007 appears to be quite commonly mentioned for maglocks ( though I respect what you say about unnecessary in most cases)
I can at least add them to increase my range of Electronic bits I have for Fire alarm repairs and the like.

Out of interest I called them "IN4xxx" ( as it was hard to read off the diode) as did you, or was you patronising me but Winston called them "1N4xxx" as do the Ebay listings, so what are they

The naming system stems from long ago where the number before the N was one less than the number of wires coming out of the semiconductor device.