Naked Science Forum
Non Life Sciences => Technology => Topic started by: CZARCAR on 03/07/2011 13:56:23
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for 110-ac, 600w, which turns on for 1-3 min & off for 10 -20 min. Can be a combination of on/off ratio as in 2on- 10 off or whatever. Has to be a repeating timer so it keeps turning on & off & on... .......thanx
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Could do that with "555 (http://en.wikipedia.org/wiki/555_timer)" timer circuits, e.g. ... http://kitsrus.com/pdf/k85_1.pdf
Switching mains electricity is potentially very dangerous.
555 timers cannot handle mains electricity but could be used to trigger a mains rated relay (http://en.wikipedia.org/wiki/Relay) or triac (http://en.wikipedia.org/wiki/TRIAC).
Consider using optical isolation (http://en.wikipedia.org/wiki/Opto-isolator) to separate the high (mains) voltage from the low voltages used in the 555 timer circuit, for safety: protects user and low-voltage components from deadly mains electricity.
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I think this timer might do it.
http://www.harborfreight.com/digital-timer-95205.html
But, it would probably be a pain to get set up, and it doesn't say what happens with a power failure.
I've used these "push-button" timers (or similar ones) which typically have 15-minute cycles.
http://www.google.com/products/catalog?q=lamp+timer&oe=utf-8&client=firefox-a&cid=7863434557746073618&ei=2KUQTpbMD4jQiQSYv_idDA&sa=title&ved=0CA0Q8wI
This one is built in.
http://www.amazon.com/Intermatic-EJ500C-Indoor-Digital-Switch/dp/B000E8VAIO
The biggest problem with these types of timers is that while 2 on, 20 off sounds like a simple idea, you probably have to program in every independent action.
This place seems to have quite a few unique gizmos. Programmable from your computer, although some are a bit expensive. I can't tell how complex the program can be though. You can download the control software if you wish.
http://www.controlanything.com/Relay/Device/KLRR120_USB
http://www.controlanything.com/Relay/Relay/CAT_RELAY1_USB
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thanx but over my head with the IC & need a magic box i guess
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for 110-ac, 600w, which turns on for 1-3 min & off for 10 -20 min. Can be a combination of on/off ratio as in 2on- 10 off or whatever. Has to be a repeating timer so it keeps turning on & off & on... .......thanx
Depending on your application and budget, you might want to look at a Mitsubishi Alpha programmable controller. They're normally used for industrial control, but it's a smallish block which runs of a 12V (I think) DC supply, and can be programmed using a computer. It's got several built-in relays which can switch mains loads, as well as built-in timers and digital I/O (and analog input if you're lucky!).
I've no idea how much they cost and/or whether there's any cost for the programming software (which is about Windows 3.1 vintage!) - but we frequently use them at my workplace in prototype/test setups.
Hmmm first meaningful web result looks like it might be $200 for the basic one, and another $200 for the programming cable [:o]. Ouch. Useful though if you've got ongoing requirements or specifications might change. Try eBay?
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If you are handy with mechanical things, you might try speeding up a cheapo 24 hour timeswitch by replacing the synchronous AC motor with a low voltage DC motor. By varying the DC voltage, you will be able to alter the total cycle time.
(Not that I've ever actually tried this myself you understand, but I think it should be possible [:)] )
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What you are looking for is a common enough part, you need to go down to an electrical wholesaler or an electric control gear supplier and ask for an asymmetrical recycler, with a range that covers what you want. Most likely to be either an Omron, Crouzet, Riken or Telemechanique part, as these are the big names in industrial controls. This would be one unit, with you needing to provide an enclosure for it separately if it is not going into something that provides protection mostly against touching live terminals. Depending on the load you want to supply you would need a contactor to provide extra current capacity, and it will also be available at the same place, with them able to give you an appropriate unit to suit both load and voltage. You can get the recycler in units that are basic analogue types with 2 dials, for each part of the delay, to ultra expensive all singing and dancing digital devices, with full programmability for the same functions at a much higher price. All depends how accurate you want the delay, and how much tolerance you worry about in the total cycle.
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asymmetrical recycler! will search ebay..............thanx
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I have a whole box of industrial plug in relays that I use for replacement parts for old equipment, there are quite a few of these in there,