Request for timer

When I was a kid, used 555 timers all the time. I would get them at Radio Shack. Now that Radio Shack mostly doesn't sell electric/electronic components where do you buy them? Especially when buying less < $10?

. Most online electronics distributors (eg, Digi-Key) will sell small lots. Or try E-Bay. I used to buy dual-555's (556?) for about the same price as a 555.

I am currently doing something very similar; I am using a 16f62x (more below for explanation). A 555 timer allows you to change the on/off cycle of both the high side and the low side of the output, if you attach two trim pots where the two resistors normally go you should be able to tune it to your liking, just hook it up and experiment. You might want to think about slaving another timer off the main one (I don’t know if this can be done with a 555 but a 74ac240 BEAM style oscillator or transistor flip-flop should work) to turn the camera on and off, but I`m not sure if that would be energy efficient with camera’s tending to go into standby mode of their own accord after about 30 seconds of inactivity. *I`m using a 16f62x programmable chip because I am attaching it directly to the camera (£20 digital camera bought years ago) and I have to navigate the options, turn on a separate IR flash module, take a photo and turn camera off and turn flash module off (wait a pre-defined time (about 28 seconds, about 1 minute or about 5 minutes) and repeat, sleep the chip when a pre defined number of photo's is reached - in this case the cameras limit 80). If power usage is an option you might want to consider using a similar (though probably simplified) set up, and if you choose to use a 16f267/8 I can supply you with the code if you want (I don't know any other chip but I suppose it shouldn`t be hard if its another 16f to transpose across) and put in some option bits on the pins for hardware setting of the time (roughly).

Yes you can alter the mark-space ratio of an astable by selecting the right size resistors. Cheers, Pat. Pending