Snubber design for relay computer - Page 1
Forum section: electronics / projects

author: LondonNight
author_rank: Contributor
timestamp: January 19, 2022, 11:43:28 am
content: 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 kickthat 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

author: T3sl4co1l
author_rank: Super Contributor
timestamp: January 19, 2022, 11:52:36 am
content: Lots of good info here:https://www.eevblog.com/forum/projects/snubber-3-different-230v-ac-motors-in-a-record-cleaning-machine/Tim

author: LondonNight
author_rank: Contributor
timestamp: January 19, 2022, 12:04:17 pm
content: Thanks Tim!

author: Ian.M
author_rank: Super Contributor
timestamp: January 19, 2022, 12:17:59 pm
content: I wonder if a NE-2 Neon bulb across each coil would be sufficient?Quote from: Mainframe Computer Room Humor

author: LondonNight
author_rank: Contributor
timestamp: January 19, 2022, 02:37:54 pm
content: A very interesting idea!!! I will look into it.

author: jonpaul
author_rank: Super Contributor
timestamp: January 19, 2022, 03:41:09 pm
content: 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 ChanceJon

author: David Hess
author_rank: Super Contributor
timestamp: January 19, 2022, 10:59:10 pm
content: 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

author: floobydust
author_rank: Super Contributor
timestamp: January 19, 2022, 11:48:41 pm
content: 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.

author: Haenk
author_rank: Super Contributor
timestamp: January 20, 2022, 08:12:47 am
content: Quote from: jonpaul on January 19, 2022, 03:41:09 pmActually 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/

author: jonpaul
author_rank: Super Contributor
timestamp: January 20, 2022, 12:58:23 pm
content: ......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-onlyhttps://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.jpgBon ChanceJon