remotely controlling 15 relays

[Ben.V.293]

I am working on a project and i need to be able to individually control 15 differant relays by remote control. I do have have much experience at all in electronics and i was hoping someone here could help me. I would like it to have a range of at least 250 feet and i would also like to find a cheap way of doing this. Im hoping i do not need anything as complicated as a first controller or anything. any help would be greatly appreciated.

Ben Van Selous

[Al Skierkiewicz]

Ben,
Questions?
1. One of fifteen relays at once? More than one at a time?
2. Cable requirements between controller and relay box?
3. What signals are you controlling with the relays?
4. What power supply do you have available? Is it separate power at both locations?
More to follow later...

[Ben.V.293]

thank you for responding

1. i would like to controll each relay individually and no more than two relays will have to be closed at the same time but the more that can be closed at the same time the better. here are the relays i am looking at http://www.radioshack.com/product.as...5Fid=275%2D248

2. I am hoping to not have any cables running between the controller and the relay box. they will each have differant power sources.

3. I am not sure what you mean. I don't know much about electronics

4. The relays will be contolling power from a 12 volt car battery. They will be actuated by regular 9 volts. The controller box will run off whatever is neccesay for the radio.

Again, thank you. I really appreciate your help.

Ben Van Selous

[Shu Song]

i'm curious, what is this project?

I think Al was asking what are you doing with all the relays.

[Al Skierkiewicz]

Once you throw a radio link into the mix you suddenly complicate things. A simple control cable with 12 wires is the simplest, no need for encode or decode. You can use logic blocks to decode 1 of 10 switch inputs to BCD, transmit that via 6 wires and then decode back to decimal at the relay box. This requires a logic power supply at each end. You could use a voltage encoded generator (i.e. a circuit that generates 10 different voltages) send it over a pair of wires and decode with a window comparator back to one of ten at the relay box. Or you can use telco tone encoding and decoding using DTMF(Dual Tone Multi Frequency). You could use that to modulate an ultrasonic transducer for hand held remote operation. Or there are a number of chipsets for remote Infrared communication available, just search the Internet for part numbers. There should be a number of books at the library on remote control you could consult. If you need to activate more than one relay at a time you need to have control over the on and off charachteristics which may require electronic latches. There are relays that latch but they are expensive. For those you pulse them with voltage to change states. I know this doesn't help much but what you ask for is a rather interesting electronic problem for designers and there are a variety of solutions based on what your needs are..

[Ben.V.293]

thank you for your help. I am building an electronic model rocket/fireworks ignition system. I already have a working prototype that uses light switches and vast distances of wire. I can indvidually ignite 45 differant fireworks all from the safety of my controll panel. I am now building a new one where the controll panel is inside of an alluminum suitcase. I was orignally going to have the wires plug into the side of the suitcase with phono plugs but i thought it would be really cool if i could do it by remote controll with relays. One of the electronics guys from my team is now helping me out and i'm learning alot. I'll post pictures of the finished product when its done.

Thank you,
Ben Van Selous

[Greg McCoy]

Be careful!!!

Your application is potentially dangerous, wired or wireless. If you decide to use a wireless system, you must be especially confident that it will only trigger when desired, and not from noise or other strange occurances

Make sure that what you are doing is legal and safe. It might be a good idea to look into systems that are already designed for this type of application. Whatever you do, make sure that you don't have rockets/explosives going off when you don't want them to.

[Ben.V.293]

Originally Posted by Greg McCoy

Be careful!!!

Your application is potentially dangerous, wired or wireless. If you decide to use a wireless system, you must be especially confident that it will only trigger when desired, and not from noise or other strange occurances

Make sure that what you are doing is legal and safe. It might be a good idea to look into systems that are already designed for this type of application. Whatever you do, make sure that you don't have rockets/explosives going off when you don't want them to.

Thank you for the advice. Safety is my biggest concern and it is also the reason i built this system. I never felt safe lighting fuses and then scurying off to safety. I have many safety features built into it such as a key switch so only i can use it, diodes to make sure the electricity only goes where its supposed to, and as another safety feature i wired it so that 2 switches must be pushed to ignite any one rocket. I had not thought of the wireless system going off from interfearance or signals from another source. Thanks for pointing that out. I'll have to do some research.

Ben Van Selous

[Al Skierkiewicz]

Ben,
I have to go along with Greg here. Wireless ignition systems are notorious for false triggers unless the system is very sophisticated and uses a data stream with error checking for ignition. Most of the systems I have seen are as you describe, wired with key lock and dual arm switches. This is the type of system used by Hollywood special effects guys and fireworks operators.
The KB9WTE at the bottom of Greg's signature is a good sign he knows wherefore he speaks on wireless.
Al, WB9UVJ

[Adam Y.]

The KB9WTE at the bottom of Greg's signature is a good sign he knows wherefore he speaks on wireless.

What is that? I am inclined to think it has something to do with ham radios but I really don't know.

[Al Skierkiewicz]

Originally Posted by Adam Y.

What is that? I am inclined to think it has something to do with ham radios but I really don't know.

Adam,
You are correct, it is an indication he (and I) are licensed hams.

[Greg McCoy]

Originally Posted by Adam Y.

What is that? I am inclined to think it has something to do with ham radios but I really don't know.

If you're interested, here's more information on amateur/ham radio:

http://www.arrl.org/hamradio.html
http://www.dxing.com/whatham.htm

[Ben.V.293]

Because of the safety hazards i've decided not to go with wireless ignition. Thanks for pointing out the dangers of it. I'll just run wires like i did in my prototype. Thanks for the help everyone.

Ben Van Selous

[Sparks333]

Good choice!
There was something else Al and Ben missed. A radio sends out radio frequecies, and a reciver puts out PWM, which is ineffecient for triggering relays. That throws a monkey wrench into the works!

Sparks

[Scott L.]

interesting project. I've actually built a model rocket launcher that can launch up to 8 rockets at the same time either manually or after a preset time. This project is posted on my website: www.personal.psu.edu/sdl162.
I have recently obtained a plc (programmable logic controller) and am in the process of programming it to launch model rockets. as for wireless you could use one laptop(remote) wirelessly connected through adhoc mode to your control panel laptop (master). u connect the remote pc using its parallel port and some programming, to remotely launch the rockets. u should be able to do upto 8 this way. u connect a 5v relay to each of the parallel port outputs of the remote pc. then u connect your input switches to the parallel port of your master pc. i'm in the process of setting a simular system up to remotely control the observatory dome on campus. hope this is of some help.