Back EMF diode

[surreysparks]

What specific diode would I need for 12v DC locks, to reduce back EMF, as when you buy them on there own there is no diode unlike the paxton stuff etc that comes with one??

 

[johnbyrne]

Hi , we must stop meeting like this. I'm not saying that varistors have no use. Just that when reducing back emf that diodes will hold it lower, I don't dispute that varistors will do things that diodes will not, Cheers

 

[tazz]

finding it an interesting debate, and you have come over in a polite and constructive manner..........next question, what would you be hoping to protect, with say a in4001

 

[johnbyrne]

Hi Tazz, I'm not looking to dodge the question, I don't have my semiconductor book to hand , although I think that is pretty bog standard diode, I don't know offhand what it's parameters are. However I will say that my experience of needing to suppress back emf was for alarm systems from years ago. lots of cmos chips all allergic to solenoid bells and not happy with relays .One job needed an OAk8 which if I remember is a gold bonded germanium diode, looked like a signal diode. Have you ever come across an alarm panel called Equaliser 3, it would play up if some used drill in Iceland. Cheers

 

[johnbyrne]

OA48 I think

 

[tazz]

Design a few of the well known alarm panels, over the last decade...lol.....from your processor or cmos to out transistor, good practice is to fit diode for emf when switching relay, chances of transistor, or cmos jumping or osolating is quite rear but the diode is there. After switching through the relay, are only other problem is high voltage from coils such as coil locks, with their emf, low voltage will not jump through a relay, but high voltages may, very rare tho....so this is where varistor comes in.....(internal relay/circuit protected by diode....external high voltage protected by varistor.

 

[johnbyrne]

I had not noticed until a few minutes before your reply the alarm connection, had bash in the eighties making our own pcbs, not really worth it, early days of ADE , their panels were cheaper, still have loft full of old panels. loved early optimal some still around, cationic for better jobs.This tablet is too small for my arrested.

 

[tazz]

I was a pcb designer for ADE and A1 in the early nighties, back in Liverpool

 

[johnbyrne]

They called seemed to be in Liverpool,ADE ctec McDonalds.I might still have an early ADE green button isolate zone two, then logic 4, optimal , great panels

 

[johnbyrne]

A1 was Omnicom?

 

[tazz]

first optima, was a bit hit or miss, they used to lock up like A1 omnicron panels....but this was new technology then using micros, this was new for us, suddenly forget logic chips....we have 8 inputs and 8 outputs, and the programmers sorted it all out, then we realised the micros needed backup chips, so was born the nvm chip, non volitile memory, this would backup the micro every sec, keeping the panel going.......little bit of history for you...lol

 

[tazz]

yes A1 make omnicron 6000, 7000, 8000, very rushed out systems

 

[johnbyrne]

I like playing with logic gates, the wonders of truth tables. later processor alarms offeredbetter function than fixed logic gates. Agree about Omnicom. First reset on scantronic putting nvm eight legged chip back in with power on a worry. Off to bed in a min, rescue dog asleep, sofa not going to be eaten tonight, Cheers

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I like playing with logic gates, the wonders of truth tables. later processor alarms offeredbetter function than fixed logic gates. Agree about Omnicom. First reset on scantronic putting nvm eight legged chip back in with power on a worry. Off to bed in a min, rescue dog asleep, sofa not going to be eaten tonight, Cheers

 

[tazz]

4000 cmos series, had a logic for every application...now to you can tell a micro what to do, less components, less space...we have to sub contract the programming out now, things moving too fast

 

[Hawkmoon]

Over my head

 

[tazz]

Over my head

Memory lane...lol...nice chat with a new member