NE555P for POSC

[kasbah]

Will any NE555 model work for the POSC? I have been building one on stripboard and have been using the NE555P. I have run in to some problems (the LDR oscillator seems to be always on and very high pitched whereas the metal contact one seems not to make a sound) and was wondering if this could be due to my choice of NE555 model.

EDIT: NE555 datasheet VS NE555P datasheet

[Jim]

always on and very high pitched

Hmmm.... Sounds like you have your main oscillator stuck on, the main oscillator is the 555 timer attached to the body contacts - this oscillator should switch the other one on and off chopping the high pitch up, if it gets stuck on you just get the annoying high pitch of the LDR controlled oscillator by itself.

Had a brief look at the datasheets, all the pins look the same and the ratings look very similar - however I've not used the NE555P before and it may act a bit different in the Posc circuit.

My first guess would be to look at removing or changing the 3M3Ω resistor, it's used to stop the oscillator from getting stuck on while your not pressing the contacts - it may be a suitable value for the NE555 but not for the NE555P (you may have to do a little experimenting)

Does the main oscillator work when you bridge the body contacts? Or do you only get the light controlled oscillator and no main oscillator whatsoever?

[kasbah]

Thanks! I have actually made it work. One of my IC's was simply faulty and I had some wiring trouble as well. Sorry about the noise. Works great now! Sounds awesome!

[Jim]

Good job! - Glad it's working....so the NE555P will work fine as a substitute, that's good to know.

[kasbah]

I have been meaning to post this for ages, ever since we did POSC workshops in the summer.

While experimenting with the circuits a bit, we found that if the top chip is a NE555P as opposed to a regular NE555 the POSC sounds much better. It is hard to describe. It seemed much crisper and more musical. I suppose this has something to do with how fast it can switch on and off.

[Jim]

That's good to know, I'll have to check one out and compare it, thanks for posting ^_^