Dub stuff

[duck_arse]

isn't the 555 timer family famous for ignoring supply voltage variation versus timing/frequency changes? isn't it?

your now de-mooted fiya switch - when open, the transistor won't reliably know what to do, the base has no reference (to ground or supply).

[anotherjim]

Yep, the timing thresholds will change in proportion to supply V change.
Although if you are thinking of getting more push from the CV if the 555 supply was lower, it might, but I'm not sure.

[Kipper4]

your now de-mooted fiya switch - when open, the transistor won't reliably know what to do, the base has no reference (to ground or supply).

And just how do I reference it? +9 > resistor >base. Base>resistor to Gnd ?


Why doesn't it know. Since it's only used as a switch does it care?
I'm not sure what you mean.
I'm pretty sure that's how I have it on the breadboard and it works.

I'll try the +v supply trick and see thanks.

[anotherjim]

I'll try the +v supply trick and see thanks.

Chip may not like more than 0.5V above Vcc on any pin. Resistance - at least 10k - in series with CV should prevent damage. Chip input may clamp CV at a diode drop above Vcc, preventing much advantage -  depends on internal chip circuit.

Why doesn't it know. Since it's only used as a switch does it care?

Having the base "floating" should leave the transistor switched off. However, it can do so slowly (too slowly for most logic circuits, but speed isn't much of an issue in this case) and it could partly or intermittently turn on due to noise pick-up and layout capacitance. The reliable thing to do is to have a resistor from base to emitter (or the supply rail nearest the emitter). This is a "pull off" resistor. The pull-off R should be large enough that it doesn't cause too much volt drop from the base control input that might prevent it switching the Q on.

[Kipper4]

Thanks gottya.
I'll start with a 22k and work my way up.

I made myself a voltage divider ~7v to try to power the 555 from. It was a big fat zero.
Youse where right Stephen.

More late night trials tonight.
Meantime I'm on holiday, so it's time to get loaded.

[Kipper4]

And then there's this.

Still waiting for these chips......

[Kipper4]

How does 50k sound.
If I look at the Q1 volts what should I expect?

[Kipper4]

with a 47k C>B resistor Q1

collector
4v mute
0v unmute

base
0v05 mute
3v8   unmute

emitter
0v06 mute
3v1   unmute


Gnd= 0v06

seems fair to me.
thoughts please.

[Kipper4]

post deleted i'll repost later

[Kipper4]

Heres something else thats much simpler to build and fun to play with a 3 mode Siren.
Based on the ne556 timer.

It's on the second breadboard. Yep I'm that sad, I have 2 breadboards going on this project.

[ElectricDruid]

Only two?! But that's just for this project right?! You've got about ten other projects on the go as well, I expect? With several breadboards each for those too? Bonus points if you're re-using spare space at the edge of one breadboard to test some random bit of some other project from some other breadboard - an envelope follower, say, or a little LFO idea, on the side of the board that contains that triple-stage compander fuzz.

I have circuits on breadboards that I can't even remember what they're supposed to do any more. And whether they still do whatever it was, or whether I've borrowed half the vital parts for the latest and greatest something else. Sigh. When will I learn?

Tom

[Kipper4]

Yer Tom.
Fun aint it.
I still have a sweller on another breadboard that needs reviewing. and the schematic updating.

I've decided to commit to perfboard and stop playing with it on the breadboard.
I does more than I expected it would. The irons hot, just about to find the offboard stuff.
The sweller has an envelope wouldnt you know.

" Bonus points if you're re-using spare space at the edge of one breadboard to test some random bit of some other project from some other breadboard."
I have done this in the past. Not this time, I organised the breadboard layout so I could put some mods in.
Good job I did I found out what as worth keeping.

Cant stop and chat for long. Those wires wont strip themselves. I got 8 pots and 5 switches in this one.

[duck_arse]

[ I've heard kipper keeps his spare breadboards in envelopes. ]

[Kipper4]

It's built and all working fine. I need to think about the boxing now.

I guess you all think my Q1 voltages are good then and the  47k BE resistor is ok.


I'm not short of envelopes.....

[duck_arse]

does your "Q1" havva collector resistor? it doesn't onya shown circuit, wid de fiya switch, mon.

[Kipper4]

Warning update
1k resistor between 555 vco out and Q1 collector

Heres the current arrangement.

[Kipper4]