OK, the circuit works great, but it fried my 555. Or at least, it stopped working properly, and when I replaced the 555, it started working again. Why would it do that? I bumped it up to a 6 V supply so that my output voltage was closer to the 4.5 I want, but I'm way below the upper limit of the 555. This is actually the second 555 that I fried on this project, but the last one was when I was messing with my original circuit.

 

Post a schematic of what you actually built, and a photo of the assembly. Most likely, there is a wiring error.

 

All right, here they are. When I replaced the 555 circuit, it went back to working as it should. R1 is actually 4.7 M.

 

There is nothing in the schematic that would keep it from working. However, with a 4.7k R1 and a 1uF C1, the pulse duration would only be about 5 milliseconds...barely a flicker. Is that what you want? ETA: I just noticed the 100 ohm resistor on the LED; at 6 volts, that calculates to about 40mA through the LED, which is too much for most. Maybe with the short pulse, that's okay, but if you light it up for a few seconds, it may burn out, depending on how much current it's rated for.

With regard to the photo, there's not enough resolution for me to tell much about the wiring. I can see that the circuit is really spread out with too many long wires.

 

Build it like this and it will work. 4.5V is on the low edge of what a 555 needs to operate.

I believe the cmos 555 will operate down to 2v.

 

No, the R1 is 4.7 mega ohms. I'll have to double check the capacitor. When working the way I anticipate, the LED stays on for about 55 seconds.

I don't think this is a CMOS 555. I am hoping to get about 4.5 volts out of the output. On the other hand, I suspect I may run into another issue. I want to power one of those singing Christmas card circuits. I can hook those up to a 4.5 volt source and get it to sing, but the one time I tried it with this circuit while it was going, it did nothing. I wonder if I may be better off with a low voltage CMOS to a transistor that provides the voltage I need, but transistors are still outside my knowledge base (sort of)

 

No, the R1 is 4.7 mega ohms. I'll have to double check the capacitor. When working the way I anticipate, the LED stays on for about 55 seconds.

I don't think this is a CMOS 555. I am hoping to get about 4.5 volts out of the output. On the other hand, I suspect I may run into another issue. I want to power one of those singing Christmas card circuits. I can hook those up to a 4.5 volt source and get it to sing, but the one time I tried it with this circuit while it was going, it did nothing. I wonder if I may be better off with a low voltage CMOS to a transistor that provides the voltage I need, but transistors are still outside my knowledge base (sort of)

My mistake; I misread your post. 4.7M and 1uF will give a pulse just over 5 seconds. If you are getting 4.5V out of the 555, then with a 100 ohm resistor, that's 25mA through the LED. So, if it's rated at 20mA maximum, it may have a short life.

As to the singing circuit, I don't know how much current they require. The 555 can source about 200mA, which seems like enough, but maybe not. If you seriously overload the 555, that could be the cause of its demise. You could add a transistor switch, but you would need to know the current required by the singing circuit in order to select a transistor.

 

I hadn't thought to do it, but I can at least measure the resistance of the singing circuit. They use three of those 1.5 V watch batteries, so I assumed it didn't draw much power, but it is a 16 Ohm speaker.

I don't know if it will drive the circuit, but my connections to it are shoddy since it won't accept solder. I will use some conductive tape and epoxy to get a better connection tomorrow.

The LED has lasted longer than the 555, but I agree that it looks over driven. It still out lasted the last 555.

 

The circuit works as is. I'll post pictures of the first device I built. I built it a bit late for the ugly Christmas sweater business, but I'll have a head start for next year. I need practice soldering and designing things.

One difficulty, is the board the Christmas card circuit is on, is clearly not means to be soldered to. I solved that with copper tape and epoxy (JB Weld). I also seem to have one circuit that I suspect is overheating.

 

heres a way to debounce your circuit and another version of your 555 circuit just for information ....obviously you can change the timing components to suit,ant the 555 is now edge triggered and debounced so just one closure of the switch will trigger it