# Simple question regarding relay

1. Jun 13, 2006

### DrKareem

I've bashed my heads through walls trying to make this work. I have a small project that is done except this part. I want to use a relays (5 pins) as switch such that when switch switches to the other end, it gets stuck there untill it is reset from an external push-button.

One of the solutions that I tried that theoretically should work is to connect the common the end of the switch with a voltage applied to it, but didn't work...

2. Jun 13, 2006

### Averagesupernova

Use the contacts to complete the circuit for the coil current. Use a normally closed push button switch to interupt this current to reset it.

3. Jun 14, 2006

### Danger

Yeah; it's called a 'latching relay'. As Average said, you just use the secondary contacts as part of the primary coil circuit. Bypass them with a parallel-wired switch to energize it in the first place, and have a second cut-out switch in series to turn it off. If further info is needed, I can post a diagram later.
By the way, both sides of the switched circuit have to be running from the same voltage (or at least close enough that the coil can handle the power from the secondary supply). If not, use a 3PST relay (6 pins) and take the 'loop' power from the primary supply through the normally unused pins.

Last edited: Jun 14, 2006
4. Jun 14, 2006

Thanks a lot guys. It worked. I basically implemented one of those laser security systems (If you bass through the laser beam, an alarm sounds) for about 3$. Contact me if you want the design, it's really simple. 5. Jun 14, 2006 ### Danger I just might do that, Dr. It would be handy for me, not as an alarm but rather a trigger for some electronic home decorations. 6. Jun 14, 2006 ### DrKareem (I'm not really a Dr. don't know why i made that name when i first registered couple of years back, i'm an undergrad student graduating in few days :p ) I used a photo resistor at the base of a BJT with another one acting for the voltage divisor. When light shines on the photo resistor (should be bright light) resistance drops to zero and BJT would be effectively grounded and thus turned off. I'm sure that's how you thought of it. 7. Jun 14, 2006 ### Danger Actually, I just abbreviated your name as I do most others because it's easier to type. I did not, in fact, think of it at all. I know virtually nothing about electronics. I can, however, follow a schematic to build something. I know that I have plans for some photocell circuits somewhere. In fact, I just bought myself one of those 200-experiment electronics kits ($10 at a 2nd hand store) to try and teach myself how things work, but W won't let me play with it in the house. (Just have to do it when she's on night shift and put it away before she gets home. ) It has a photo emitter/detector set included, and an instruction book.

8. Jun 14, 2006

### Averagesupernova

Can you describe that kit for me danger? I have one from many years ago and had alot of fun with it. I'm wondering if they are the same. Did you get the manual for it?

That's Averagesupernova to you buster. :tongue2:

9. Jun 14, 2006

### Danger

Bite me. And the fight is on...

It's the Science Fair 200-in-1 Electronic Project Kit. There is indeed a manual, the copyright for which reads 'c 1987 InterTAN CANADA LTD.'

10. Jun 15, 2006

### Averagesupernova

Is the battery holder in plain site or is it underneath?

11. Jun 15, 2006

### Danger

I haven't used the thing yet; just glanced at it when I first got it. I believe that it's a 2 x 'D' cell unit on top in the far right corner, but I can't be sure until I look again tonight. I'll probably bypass it and use a wall adapter instead.

12. Jun 15, 2006

### Averagesupernova

Umm, no. Not likely the wall adapter will work. Most of those projects need clean DC power. Not something with ripple on it. Also, some projects need 3 volt supplies, some 4.5, some 6, and some 9. Most likely it is 6 AA batteries. I'm just wondering which one you have.

13. Jun 15, 2006

### Danger

Hmmm... I hadn't thought of the ripple. Anyhow, I'll look as soon as I get home from work in a couple of hours and let you know right away.

14. Jun 15, 2006

### Danger

Hi, I'm back; did you miss me? :shy:
Anyhow, here's a picture of it. You're right; that case is for 6x 'AA' batteries. Sorry about the picture quality. I don't really know how to use this camera for close-up stuff.

15. Jun 15, 2006

### Averagesupernova

Ok. That's the one I thought it was. I had one that is older than that. Mine had a dust cover and the batteries went in the back side under a cover.

16. Jun 15, 2006

### Danger

Really? Given your advanced chronology, I would have expected it to have vacuum tubes. :tongue:

17. Jun 16, 2006

### Averagesupernova

Pot.... kettle..... black....

18. Jun 16, 2006

### Danger

:rofl: [color=#eded]....[/color]

19. Jun 16, 2006

### Averagesupernova

A tube set would have been kinda cool though. I have little experience with tubes. I guess there is nothing stopping me now from doing some tube projects.