Author Options:

Relay Logic Answered

I have a fetish for antiquated technology. Stuff like vacuum tubes, transistors, electro mechanical devices, and of course relays used to run things. I did a few searches here on Instructables on relay logic and found nothing so I thought I'd start a forum on it. 

Most of the earliest computers ran using relays. I love how they sound, clickity - clack. In a way they seem more alive to me than todays silent electronics, and dead boxes, There's just something cool about a machine that you can hear working instead of dead silence, maybe I'm just a old fashioned. 

Anyway, I have a limited knowledge using relays for adders, if, and, or, gates, etc. but I'd like to learn more. I did however make a clock circuit using only relays and capacitors, and I have a video of it here...


I based that circuit (after lots of pondering and experimentation) on the clock in this relay computer here.


My relay clock was really unstable and would stop by itself quite a bit. I'd like to figure out how to make it more stable. Also, I'd like to do some more experiments... Anybody else have any interest in this subject? Or have any experience making small bit relay computers, or relay control systems for robots, etc?

By the way here's some other cool relay run computers and stuff.

Another Relay computer

Relay counter thing.

Mechanical pong game - run on relays


.  To play with relay logic, without the expense of physical relays and the hassle of hard-wiring, look into "ladder logic" simulators. Great for designing and testing circuits before building.

Nice, thanks for the info. NachoMahma... I just found one I just downloaded and am messin with, a simple logic simulation program I mean. While looking up "ladder logic simulator" led me to "Programmable Logic Controllers", which is fascinating as well. Thanks again!

.  I used to program Allen-Bradley PLC-2 and PLC-5 systems using A-B's 6200 software (ladder logic). That was ten years ago, but I should be able to help you with basic questions.

Thanks NachoMahma, I appreciate the lending hand! yea I've been looking for a good ladder logic program, after you had mentioned it. I'm on a mac, and also Linux so in some ways kinda limited since most of what I've seen is Windows based..... However, after a bit of an extensive search, I did find this program called Atanua which seems pretty good, it's here... http://sol.gfxile.net/atanua/ Seems to do what I want for problem solving basic ladder logic, and as a bonus shows workable ICs which could then be worked into actual projects later on. As I mentioned I'm more interested in relays for the time being, but my interests change almost daily sometimes so this program seems like a good starting point. Anyway, the logic behind ICs, and relays are the same, I just like the chunky -clunkiness of relays.

Check out the most recent issue of MAKE. There's an article on PLCs with a brief digression into ladder logic.