Snubber design for relay computer

[LondonNight]

I need advice on the best way I should go on to design an (I believe RC?) snubber network for a relay computer. Im building a version 2 of my current relay computer, and the contacts on my first computer are dying because of the flyback inductive kick that the relay coils provide. No diodes/transistors allowed. 

What values are the best for the snubber? Should I measure the inductance of the coils?

Relays are all JQC-3FF 12V

[T3sl4co1l]

Lots of good info here:
https://www.eevblog.com/forum/projects/snubber-3-different-230v-ac-motors-in-a-record-cleaning-machine/

Tim

[LondonNight]

Thanks Tim!

[Ian.M]

I wonder if a NE-2 Neon bulb across each coil would be sufficient?

Achtung!
Alle touristen und non-technischen lookenpeepers! Das machine is nicht fur fingerpoken und mittengrabben. Is easy schnappen der springenwerk, blowenfusen und poppencorken mit spitzen sparken. Das machine is diggen by experten only. Is nicht fur gerwerken by das dummkopfen. Das rubbernecken sightseeren keepen das cottenpicken hands in das pockets. Relaxen und watchen das blinkenlights.

[LondonNight]

A very interesting idea!!! I will look into it.

[jonpaul]

Bonjour, BRAVO for the project, like the first relay computer  Zuse Z1 in Germany 1936!

https://en.wikipedia.org/wiki/Z1_(computer)

What relay and supply V will you try?

1/ DC Relays can have high inductance 100s mhy...Hys this the stored energy is L *  I(exp 2), perhaps some joules. THe sudden break of current causes a hig voltage limited only by the insulation and stray L, C.

2/ NE-2 and other neon's are rated for ~ 10 Ma and not high I pulses, but special calibrated gas spark gaps (CP Claire, Siemens) were intended for such use. However hose are costly and hard to find.

3/ before semiconductors we used  RC snubber or a Zinc Oxide protector, ("MOV")

4/ For a small relay   5..24 VDC,  try a 10...100 nF plastic cap in series with 100 Ohm 1/2W R.

Like to see schema and photos when its done.

Bon Chance
Jon

 

[David Hess]

Motorola wrote an application note which covers it in detail.  While they were thinking of thyristors, it applies just as well to relays.  I have included it below as an attachment.

AN1048 - RC Snubber Networks For Thyristor Power Control and Transient Suppression

[floobydust]

Consider using a resistor across the relay coil, if you want a purist solution. This is done in automotive because a back-EMF diode fails the reverse battery requirement. So you will find a 680R-1k resistor across a coil instead, which wastes some energy as heat but greatly reduces the back-EMF.

[Haenk]

Bonjour, BRAVO for the project, like the first relay computer  Zuse Z1 in Germany 1936!

Actually the Z1 was a *mechanical* computer, no relays involved. Which makes it even more impressive, I think.
The following designs were state funded and as a military project, he had access to enough of the very expensive and quasi unobtainium relays, so he could go "electric".

If you happen to visit Berlin, check out the "Technisches Museum", they have some nice Zuse exhibits (and plenty of other vintage electrical and technical stuff - worth a visit):

https://technikmuseum.berlin/ausstellungen/dauerausstellungen/informatik/

[jonpaul]

......Actually the Z1 was a *mechanical* computer,

Check the Babbage Difference Engine and Babbage Analytical Engine for 1830s mechanical computers....totally mechanical and no electricity!

https://collection.sciencemuseumgroup.org.uk/objects/co62243/difference-engine-no-1-difference-engine-no-1-portion-only

https://www.computerhistory.org/babbage/engines/

full working machine realized by Dr Doron SWADE at the Science Museum in London 1991.

https://en.wikipedia.org/wiki/Difference_engine#/media/File:Babbage_Difference_Engine.jpg

Bon Chance

Jon