Alright, where to begin with this? My son is training to box. When he trains at home he does whats called bursting drills. At the gym they have a light that kicks on every so often. Im not spending 240.00 on this type of light. What my son uses now is a kitchen timer that he got from the dollar store. I would like to add a 9 volt battery for the light so that when the timer goes off after how many minutes he set if for the light will come on. Im not sure how to wire this or even what parts to get. Could I use a transistor to switch on the light. The timer uses one AA battery. This is a new hobby for me as im retired and it keeps me out of my wifes hair. Any help would be appreciated. Thanks for your time, Dave.

 

My martial arts class had something similar, it was pretty expensive too as I recall.

Break down what you want a bit. You want a light that comes on after a delay, stays on for another delay, and then turns off?

It might be possible to connect to a piezo speaker in the timer if it has one.

It might be easier to build one from scratch.

Define exactly what you need, assume we don't have a clue, so break it down.

 

Thank you sir. My son has a plain old kitchen timer that he bought from the dollar store. He programs in how many minutes he wants and then starts his drill. After however many minutes, the timer will beep. I want to make that timer light up a 9 volt light that I have. When the timer goes off and the alarm beeps the light goes on too. He really needs both sound and light, cause the gym is loud. Now ive tried using a transistor as a switch to turn on the light thats connected to the 9 volt battery. What I need is kitchen timer-goes off-piezo buzzer kicks on light. Thanks for your time. Dave.

 

Can you make a schematic of what you've tried?
If you want to buy an adjustable timer with a relay output, try one of these.
http://www.altronix.com/index.php?pid=2&model_num=6030

 

What I did was wire the base of a transistor to the positive side of the piezo buzzer then the others through the 9 volt battery out to the light. I thought the transistor would act as a switch. I dont think the buzzer puts out enough power to switch the transistor. Thanks Dave.

 

....then the others through the 9 volt battery out to the light....

This doesn't make sense. Not enough detail. Can you draw a schematic of what you did?

Ken

 

He just wants a calibrated monostable, or something to amplify the piezo signal to trigger a light. I've thought about doing something like that myself.

So how easy is this piezo to get to? If you can attach several wires to it (both sides) the rest is gravy.

 

How he gets the transistor to switch depends on whether the buzzer is driven by an NPN (sink) or PNP (source) transistor. Though I haven't heard back from the OP another thread, you might find it interesting. http://forum.allaboutcircuits.com/showthread.php?t=39785 It's on a similar attempt.

Ken

 

The piezo buzzer is extremely easy to get to. I dont know if I should use a transistor or a relay or both. The timer like I said runs on one AA battery. I guess when the buzzer goes off there isnt enough voltage to switch on the 9 volt battery to turn on the light. This is a new hobby for me. I was told that if I hooked the base of the transistor to the positive side of the buzzer. Then wire the collecter to the positive side of a nine volt battery. Then wire emitter to the light itself and the negative of the nine volt battery also to the light it should work. But it doesnt. Thanks for your time, Dave.

 

You'll need some kind of amplifier, doesn't have to be a transistor but that is the best bet. I'll give you some ideas to try. We'll try a simple one first. You have to have battery capable of driving whatever light bulb you want to use. If you want to light a 120VAC bulb we can do this too.

I won't guarantee this will work, but I give it good odds. Vcc = 12VDC, the transistor is a TIP100 or equivalent, they are very common, but it isn't critical by any means.

If this works, and you want a AC light (120VAC) let me know, a simple upgrade for it exists (something called a SSR, a solid state relay).

 

Thank you sir, i'll try that. The light is just a regular 9 volt lightbulb. Bright enough to get my sons attention when the timer sounds off. Off to the bench. Thanks for your time, Dave.

 

Polarity does matter. Make the positive signal goes to the resistor.

 

Ive tried it two different transistors. The first one nothing happened when the alarm went off. The second one, the light was on very dim the whole time. Thanks for your time, Dave.

 

OK, there are other approaches. Do you have a DVM? We need to measure the voltage out of that pesky speaker.

Transistors have to have a signal bigger that 0.7v to work. This is where it is breaking down. We have to put a preamp on the sucker.

Are you willing to breadboard circuits on a protoboard? This would be my next approach...

<drawing>

 

Bill, I found a video on youtube that utilizes the same kitchen timer. The kid made a timer detonator out of the thing and put the whole thing in a altoid tin box. When the timer runs out on that it lights up a christmas tree light. I asked for more information but he told me he didnt share information. But thats exactly what my son and I want. The speaker puts out 20 mV. Thanks again for your time, Dave.

 

Could you post the link so other folks could benefit?

 

I guess I should have done that in the first place. If you search- formatc2 kitchen timer on youtube. Thats what im trying to do more or less for my son.

 

Attached are a couple of circuits to connect an alarm piezo to an external circuit. I have done this, but with the piezo buzzer replaced with a resistor.

Ken

 

Yes the first one worked! I wonder if thats what that kid used on youtube to accomplish more or less the same thing. Thank you all for all your help. Thanks for your time, Dave.

 

Could I use a SCR to accomplish the same thing? Im going to try a different digital timer and see if I can make that one work.