Sequantial 220V timer for 6 outlets (cold smoke generator)

Hello members! I am trying my luck with this problem:

I have 6 pcs of 220V/300W small 70x120mm heater plates. Straight from China and each working nice.

I am trying to build a cold smoke generator. One heater with a wood disk on top creates smoke up to 2 hours. Not much time to sleep if you intend to use it 24-48 hours per one batch of fish or meat.

Crude version would be 6 mechanical timers, each attched to a heater plate. Lots of cables and not so neat.

I would like to have a timer contoller, mains coming in and 6 outlets which each gets power 2 hours and rotating to next outlet.

If there are ready close-enough solutions, links much appreciated. List of specs for timer chips/relays most probably go way over my engineering skills, however could be useful if I find someone for the soldering part.

Suggestions?

Harri
Chiang Mai, Thailand

Hi,

There are PLC controls.
Easy to program.

I don't have much experience how many systems meet your requirements ... but it sounds a SIEMENS LOGO could help you.

Klaus

A single 4017 IC (decade counter) can turn on your heaters, one at a time, in sequence.

The IC has ten output pins, although you would only need 6 pins, each controlling a relay.

Apply a pulse to the input pin every 2 hours. Each relay will turn on for 2 hours, then turn off as the next one turns on.



That is the simple part. You'll need support circuitry. You'll need to create a pulse every two hours. It will require more than a 555 timer IC. The 555 is excellent to generate a time period of a few minutes. However a two hour timing cycle is unwieldy and not reliable for a 555.

Additionally the relays probably cannot be energized directly by the 4017. I believe it's necessary to add a transistor to do that. You'll need 6 transistors and 6 relays.

You could try to use a 74HC5555, it is a 555 with a internal divider for long time periods. If you set it to 17 bit (131,072) and use a 1 KHz oscillator you would get 2.184 hours, 1.1 KHz would be 1.96 hours.

You would use the Q output to drive Bradtherad's decade counter and use the 74HC5555 non-retriggerable mode. Meaning that the 2 hour period could not be extended every time you hit the go button.

The problem i see is that you really need a astable multivibrator not a monostable. After the first 2 hour timeout the monostable will sit there waiting for another input to tell it to start another 2 hour timing session and advance the 4017 counter.

That's the problem with these "simple" circuits. They snowball quickly in complexity. The quick dirty fix is feed the monostable with a regular 555 astable circuit running say every 30 seconds. So the monostable running in non-retriggerable mode will ignore the multiple input pulses until it is done timing and then it will retrigger for another 2 hours.

Of coarse there are other practical matters like the power switching with the relays that must be addressed and a power supply and a box etc.

This is a small project in itself and some electronic design knowledge is necessary.

The best answer may just be get a low cost programmable logic controller as mentioned if you can find one with at least 3A output relays. 300W/220 vac = 1.36A, and for a long life time use 3A or higher rating.