Single momentary button relay selector - Page 1
Forum section: electronics / beginners

author: Spemo
author_rank: Regular Contributor
timestamp: October 28, 2018, 07:10:28 pm
content: Hello,I am trying to figure out a way how to build a circuit.My goal is to have a single momentary switch to select or "scroll" trough lets say 6 relays -so if I push the button , it turns off the first and on the second relay , press it again, it turns the second off and the third on, and when it reaches the last one to start over at the first one (push -> 6th off , 1st on).Now I'm looking to do this with relays only, I don't want to use microcontrollers or ICs or anything like it. just relays, diodes, maybe capacitors and wires.I don't have any problems building this with 200 relays just to do this.The relays I'd like to use are simple 8 pin non latching relays with 2 contacts ( I put an image of the relay configuration into the attachment )I hope this is somewhat understandableThank youSpemo

author: tpowell1830
author_rank: Frequent Contributor
timestamp: October 28, 2018, 07:46:59 pm
content: Hi Spemo, welcome to the forum. I will think about the electrical logic to do this, it will be a bit complex. Is this a homework assignment? What will this be used for?EDIT: Your relay is a double-pole, double throw, or known as a DPDT.

author: Spemo
author_rank: Regular Contributor
timestamp: October 28, 2018, 08:09:50 pm
content: Hello tpowell,this is not a homework assignment, just a small project for myself, so there is no time limit. The use for this, I don't really know yet, maybe some kind of counter or something like that...This relay logic just fascinates me, I mean I mostly understand transistors and such, but I find a lot of beauty in relay logic... You know you push a button and you hear the circuit do its thing. And I do have a small history of blowing up sensitive electronics - so I try myself in this electric-mechanical parts.Thank you for the information on the relays.

author: Gregg
author_rank: Super Contributor
timestamp: October 28, 2018, 11:52:46 pm
content: The first thing that comes to my mind is a stepping relay kind of like this:https://www.ebay.com/itm/NOS-Olson-10-Position-Electric-Stepping-Relay-SW-843/292783669968Old dial phone systems and some other old style equipment use them, maybe you can find a surplus outlet near you.

author: Spemo
author_rank: Regular Contributor
timestamp: October 29, 2018, 03:48:18 pm
content: this looks interesting - quite pricey though and I cannot find anything in that direction with shipping to germany... That's why I thought maybe there is a way to use DPDT relays

author: rstofer
author_rank: Super Contributor
timestamp: October 29, 2018, 05:37:05 pm
content: You're going to find that building sequential circuits with standard relays is a very difficult proposition (just call it impossible with standard non-overlapping contacts). Given 3PDT with make before break contacts, it might be possible. The idea is that when a relay is energized it does two things: First, it locks itself in and 2d, it opens the circuit to the preceding relay which is what enabled it to become energized in the first place. This is why you need overlapping contacts (make before break). The relay needs to lock itself in before it de-energizes its predecessor.In short, a relay is energized when the button is pushed and its predecessor is energized. It locks itself in until its successor is energized at which time it drops out.Without spending any time on it, the 3d set of contacts combines to build a chain of NC contacts which will initialize relay 1 at power up. There may be some other way to do this. I haven't thought it through... The relays will all initialize to OFF, we need some way to get the sequence started.The complexity of designing sequential circuits with relays is one of the reasons we moved to stepping relays and, ultimately, Programmable Logic Controls (PLCs). This type of thing (weird relays with odd contact arrangements) was common in the telephony world, they had control over the design of their relays. They could have as many contacts as they wanted, they could be overlapping or not and the designers were really smart. I spent a few years working on a PBX that was all relays and quite a few cross-bar relays for the actual connection. It was an amazing design!You may get lucky and find some reference material on Google or, perhaps, Alibris.com. There used to be books on relay circuit design - back about 50+ years ago. I spent another few years in the aerospace industry working with automation prior to the advent of the PLC. It was sometimes a challenge.

author: alsetalokin4017
author_rank: Super Contributor
timestamp: October 29, 2018, 05:59:56 pm
content: Uh huh. Sounds hard all right.OR:You could simply use a CD4017 decade counter chip, with each output feeding a bipolar transistor whose function is to switch the associated relay coil. Clock signal for the chip provided by the momentary-contact pushbutton. Can handle up to 10 relays on one CD4017, or as many more as you like by cascading more 4017 chips.Like this, but simply a push button instead of the 555 astable clock circuit. You could use NPN transistors in a lowside switch arrangement for the relay coils.

author: spec
author_rank: Frequent Contributor
timestamp: October 30, 2018, 02:12:32 pm
content: + SpemoAttached is a schematic for a three-stage relay ring counter using relays, diodes, capacitors, and resistors. The circuit is based on bistable latches, where a relay is either off or is held on by switching its coil to the 5V supply line using its own relay contactsAlthough only three stages are shown you can have as many stages as you like.At any one time only one relay will be energized and all the other relays will be de-energized.The STEP SWITCH (SS) is spring biased on. To step the ring counter just press and release the SS.When the circuit is first powered up, the INITIAL ON SIGNAL (IOS) goes to 5V momentarily and turns on stage #1. You can change which stage comes on first by removing the IOS from stage #1 and connecting it to any other stage at a similar point.The circuit is designed to use the parts shown on the schematic. The relay has a 5V, 40mA coil and the contacts are double pole, double throw (DPDT).The diodes are Schottky types, chosen for a low forward voltage drop and low reverse leakage current.The capacitors are high-quality aluminum electrolytics of 10V rating (a higher voltage rating is also suitable).All components are through-hole and are available from DigiKey UK in one-of quantities for the prices shown (UK pounds including VAT). DigiKey have an operation in Germany too.The relay ring counter was a ticklish design and has not been built and tested, so I would be very interested to know if it works OKDatasheets:Relay, Kemet_ EC2-5NU 5V_DPDT_through hole (£1.48)https://content.kemet.com/datasheets/KEM_R7002_EC2_EE2.pdfCapacitor, Rubicon PX Series, aluminum electrolytic, 1000uF, 10V through Hole (£0.36)http://www.rubycon.co.jp/en/catalog/e_pdfs/aluminum/e_px.pdfDiode Schottky, ST BAT48RL (£0.40)https://www.st.com/content/ccc/resource/technical/document/datasheet/b2/2f/2a/0c/8b/b5/46/a3/CD00130229.pdf/files/CD00130229.pdf/jcr:content/translations/en.CD00130229.pdf

author: Spemo
author_rank: Regular Contributor
timestamp: October 31, 2018, 10:18:11 pm
content: Hello spec,thank you for your idea, it looks promising.I too came up with something, which should do what I am happy with.A few years ago I ran into a website which provides a little program to build circuits and simulate them.Link to circuitPlease let me know if the link doesn't work. Also, the program there is using a lot of CPU power - so it might run slower than what it was originally set to (on a I5-3470).The "Clock" is set to 1Hz , 50% on/off time (this could be realised wit ha small 555 circuit.I know there are a lot of relays and parts in there, but according to this program it works... The overlapping of the lights don't bother me much.Now the thing is, I was planning to order all the parts from china, for the price of one of these relays here locally I can get 10...as long as they work I don't care much (and I haven't had any issues so far).what do you think?

author: spec
author_rank: Frequent Contributor
timestamp: November 01, 2018, 03:16:03 am
content: Hi sp,No problem about doing the relay ring counter schematic.The animated simulation worked fine- wow, that circuit looks complicatedYou are asking about buying components from China etc. Well I have bought a load of components of all types from low cost outlets with no problem. But there are certain components that are risky: batteries, power transistors, and large electrolytic capacitors, for example.Good luck with your experiments. Many years ago, in the lab at work, a couple of us knocked up a ring oscillator using some large 10kV relays- you should have heard the racket!Don't forget to let us know how you get on

author: Spemo
author_rank: Regular Contributor
timestamp: December 01, 2018, 03:36:50 pm
content: I ordered all the parts I need for a "small" project - a clock.104 DPDT relays , loads of diodes, LEDs, trimpots, transistors - everything added up about 1275 parts to put together.I will put the relays into sockets, just in case it doesnt work out, since relays are not easy to desolder with the limited tools I have without damaging them.I'm planning on using a 555 to generate a 1Hz signal for now, maybe I'll find a way to generate it reliably with relays and capacitors.Everything will be on perfboard, with loads of wires.The hard part will be adjusting the timing, so everything keeps going smooth, there will be 50 trimpots to adjust! I decided to do this since I can't trust the ratings of those cheap chinese relays, the capacitors varying in capacity. Maybe, if I ever get to do it again, I can replace the trimpots with resistors - making it a little bit cheaper to make.I will try to make one or more videos of the construction, adjustment and everything else.If all fails, I'll have 115 relays to play around withI have made progress though - I managed to build the key element of the design, the delay circuit, which delays the turn on of the second relay once the first one is powered on. It worked well and was easy to adjust. It also allowed me to get a general idea at which resistance the trimpot should be set before putting it into the circuit, also, which is a big concern, the size of everything on the perfboard.So now, I just have to wait for everything to arrive, sadly I can't do anything until everything is here.If anyone is interested, I will upload some pictures of the circuit design, and a list of things I ordered for this.A long time ago I found a program that allows to build circuits on perfboard, route the "cables" and everthing, although I don't know how comprehensable it is for anyone else.I will keep you updated!

author: Spemo
author_rank: Regular Contributor
timestamp: January 04, 2019, 06:33:59 pm
content: Ok,this is what I used the circuit for. It actually worked outA relay based clock. All it does is counting 1Hz pulses.All the counting is done by the relays, only the 1Hz signal is produced by a crystal, CD4060 and CD4027, and a 555 to reset at 24 hours.Thank you for your help!

author: soldar
author_rank: Super Contributor
timestamp: January 04, 2019, 08:35:57 pm
content: Wow! Very impressive!

author: spec
author_rank: Frequent Contributor
timestamp: January 06, 2019, 01:52:57 pm
content: Great to see a project actually working- nice job