timer switch?

Question

I have one of those kitchen timers. I wanted to convert it into a timed switch, is there any way to do that. If so can you give me instructions.

i dont want to buy one.

it's electronic

Answer 1

Believe us. By the time you have screwed around with this for a couple of hours, you will want to buy one.

If you are talking about a :"knob and bell" type of timer, you should start by removing the dome of the bell. Then you get down on your hands and knees and pick up all the tiny little parts that fell out when you got the bell off.

After you have laid out all the parts on the table, you figure out how to put it all back together so that the timer will run. That's when you discover that one or two of the most important parts are missing.

So you get back down and look for them some more. By now you are nursing a bump on your head from raising up while you are under the table.

If you can find the missing parts, you try reassembling the mechanism. If you can't find them all, you embark on the heroic process of making a replacement for the missing part.

Now you have it back together. Try three or four different approaches, and you will find a way to reassemble it so that it runs.

Now you will notice that there is a clapper that strikes the bell (when the bell dome is in place) when the timer reaches zero. There is an arm that "cocks" the clapper when the knob rotates through about the first 5 minutes.

You can figure out some way to attach a set of contacts to the clapper. The simplest way is probably to epoxy a magnet to the clapper and set up a reed switch so that the magnet activates it when the clapper moves. If you study the way it operates, you will see what we mean.

You could also use an optical notch or make a pair of direct contacts out of a strip of phosphor bronze and a strip of nickel silver. There are all sorts of ways to set that up by making a framework that holds the contacts in the right place. By this time your head will really be throbbing.

Be careful that you don't accidentally loosen the screw that came loose when you first took the bell off and that you painstakingly re-installed when you were figuring out how to put it back together about three hours ago.

By now the realization will be overwhelmingly strong in your head. You will hear it between the throbs. What is the realization? That you should go out and buy a timer switch, and throw this one in the trash before the parts get scattered again.

Have fun.

Answer 2

There are many types of kitchen timers. I'd assume you are speaking of one of those mechanical timers that has a knob set to the number of minutes and which rings a bell as the knob returns to zero.

1) The most reasonable "engineering" answer is to use a timer with built in switch contacts; however, you have made it clear that is not what you are looking for.

2) The next method that I can think of off the top of my head would be to use a micro-switch arranged so that the knob of the switch activates the switch as the timer approaches zero.
Note if you have an old broken down printer you will most likely find a used micro-switch inside. They are often used to detect if there is paper in the printer. Some old computer mice have suitable switches inside.
http://en.wikipedia.org/wiki/Microswitch

Answer 3

There has to be a place to trip the bell at the end of time. One wire would be connected to the clapper and another to the bell. Vibration will be a problem and this will only give you a timed off cycle. More complected to make a timed on cycle unless you added another relay.
If this is a digital type timer there should be a connection you can make just by doing a little searching with an electrical tester.
You don't want to hear it, but it is cheaper and safer to buy the component you need. Your project though.

Answer 4

,every electromechanical timer switch has normally open or normally closed contacts and a common. this changes state when the timing is over. pls. consider the current rating of the contacts to avoid carbon deposits on the contacts.depending on your logic and design theory you need to either use the normally open or normally closed contacts with the common.

Answer 5

I can't even think about building one from scratch, or using an existing egg-timer for this price (US$10):
http://www.radioshack.com/product/index.jsp?productId=2102613&cp=2032060.2032337&allCount=31&fbn=Type%2FTimers&f=PAD%2FProduct+Type%2FTimers&fbc=1&parentPage=family

.

Answer 6

Easier and cheaper to buy one.