I just finished making an art piece and after I made this video, the circuit stopped pulsing after a few seconds of being on. The video is here:

http://youtu.be/5wIhyV-lBzA

As you can see, it's a wire sculpture with a electronic circuit inside. I tried resoldering the connection points and it worked, until I tried to put it together again and the whole thing went dead. So now, I'm trying to replicate the circuit, but I'm having trouble with the duty cycles. In the video, the duty cycles are about 50% and high and low are about approx a little more than 1 second each. However, I replicated the circuit exactly (quadruple checked the connections), and the duty cycle seems to by a lot higher, with a high of 1 second and low of maybe 0.1 or 0.2. Why might this be?

This is the circuit I used:

I actually used a BC478 and instead of the 33k, I used a 10k pot and added a switch. Everything else is as the schematic reads.

I saw Bill's throbbing LED circuit and plan on trying to make the first one with the 50% duty cycle. What should the resisters be to get about 1 second of high/low time?

Also, don't know if this is possible, but could a capacitive on/off switch we added to the circuit so that by touching the wire sculpture the piece would turn on and off? Thanks for your help and contribution to modern art!

 

I love concept circuits. I also like striking visual effects. I will be glad to help with whatever you want to do, I'm going to reread the above a few times to see if I understand what you are asking for.

I also tend to be a draftsman for this site. I don't do simulations, but I make pretty schematics, and some of them even work!

Looking at the differences between yours and mine I used something called a Darlington pair. It is a way of make two transistors into one virtual super gain transistor. The input impedance on mine in in the order of several meg-ohms, whereas yours is a few kilo-ohms. It is where yours is breaking down.

The 9V power supply voltage is also important, though for other color LEDs you may want to tweak the power supply voltage. When you figure the max and min voltages the LED circuit sees it makes sense.

I have seen capacitance circuits around, but I don't have any schematics handy. Ever use tactile switches? I have a schematic for a 555 that will toggle on/off with a simple push button, tactile switches are very small and have a nice click feel built in.

The formula for the 555 Hysteretic Oscillator is simple,

F = 0.7/ (R C)

It will be close enough to 50% that you will have trouble telling the difference if you use my schematic. If is funny, I didn't notice I had drawn the formula until I was basically finished with this post.

I am using a computer where I am limited on what links I click, so I will have to wait until I get home before looking at the You Tube video. If you wire a sculpture using my schematic post a video and I'll do a wiring check.

 

I think it's going to either be the capacitance touch switches or just a normal toggle in the back. I think the capacitance touch works better with the piece because you're literally making a connection with the piece.

Also when you get home, take a look at some of my other electronic pieces. I like to play with ideas, and wit. So far, the first two pieces are just a 555 astable with LED/speaker output. The Excitable Woman, my most ambitious piece so far was a lot of different premade components put together and soldering a few components together. So here they are:

You Sound Nuts!

Rowr!

The Excitable Woman

Also with the frequency calculation, which R does R stand for? R1, R2, etc? Sorry, I've been only looking up simple circuits so I haven't dealt with formulas and things like that, but I think now is when I will be starting!

 

The Excitable Woman gave me a good chuckle.

There is another chap here who likes to make Dr. Who props. The From Four Twenty is a pseudo random 20 LED flasher you might like sometime.

I suspect if you do an advanced search here for capacitive switch you will get plenty of hits. Our regular search function doesn't work very well I'm afraid.

The R in the formula is the two resistors R1 and R2 added together.