40106 Oscillator - Can't get it to work

[sub2d]

Hello there. Just dipping my toe into the water of electronics, and I appear to have got off the starting blocks and run straight into a brick wall.

I'm trying to put together a very simple 40106 oscillator, but it won't make any sound for me. I have:

- 9v connected to power bus and ground
- Power to pin 14 of the 40106
- Ground to pin 7
- Capacitor from pin 1 to ground
- Resistor between pin 1 and 2
- PC Speakers/Headphones connected to pin 2 and ground

Every video or guide I check on this seems to show the same set up, and I should be getting a tone of some kind. I plan to build on this with more and more later on, but I can't even get any noise at all at the moment.

Any idea what I might be doing wrong?

I read somewhere that the 40106 can't output straight to a speaker and needs to run through some kind of amp. Would my mains-powered PC speakers count?

Any advice would be massively appreciated.

 

[jpanhalt]

This is one of the better references, not video or YouTube: https://www.electro-tech-online.com/custompdfs/2012/03/AN-118-2.pdf

What value of resistor and capacitor are you using?

Try another odd-number inverter circuit (i.e., 3)

John

 

[sub2d]

Thanks for the quick reply. Really can't stress how much I appreciate it. This has been doing my head in for the last week! And cheers for the link to the PDF - checking that out now.

Capacitor: 100nF / 0.1uF
Resistor: 100k

When you say to try another odd-numbered inverter circuit, do you mean for the speaker output or something else?

 

[audioguru]

Your choice of resistor and capacitor will create a frequency of about 200Hz if the Schmitt-trigger oscillator drives a power amplifier with an input resistance of 10k ohms minimum.
You forgot to tell us the supply voltage. It should be from 3V to 18V.

[mod_edit: critiquing a members advise should be backed up with an explanation at least.]

 

[sub2d]

Oops, so I did. Running off a 9v battery. And thanks for clarifying about the odd-numbered inverter. Just been randomly poking my speaker into various pins for a while now!

I'm a complete beginner at this. I assume a frequency of 200Hz should be audible? And I'm afraid I have no idea what the input resistance of my speakers would be!

I take it that a single speaker ripped out of kids musical toy wouldn't work at all with this oscillator then? Do I actually definitely need to run it through my mains-powered PC speakers?

 

[jpanhalt]

All of us are subject to "target fixation" when trying to troubleshoot something that should, but doesn't work. We just don't see the obvious error.

There are several ways to deal with that. One is to take a break. Another is to try a different approach. It is for the latter reason that I suggested making a different circuit, i.e., the three-inverter circuit. It will/should also work with Schmitt inverters. Once you get something working, then go back to your original design, and the error will probably be obvious. I went through that same process during the past two weeks trying to find a bug in a program.

Regards,

John

 

[sub2d]

I appreciate any effort to help, and you have both been genuinely helpful.

I'm happy to report that I got it working in the end (but this forum seemed to be having a server error at the time so I couldn't reply). I think it was down to the resistance being too high, which I assume ties in with what audioguru was saying about CMOS not being able to drive a load lower than a 4700 ohms. Maybe. I have no idea, but playing around with the resistor and capacitor combinations seemed to be the fix.

Anyway, I spent the night fitting it into a tiny project box and I have now officially made my first "synth". I even threw a power LED and (sort of) volume control on there for good measure.

Thank you so much for the help!

 

[jpanhalt]

Hi sub2d,

I am delighted you got it to work. If you want a little more current, the outputs of your inverters can be paralleled, as shown in this link for an inductor test bench: https://www.dos4ever.com/flyback/flyback.html#ind2

A mosfet amplifier can be used for even more current (also shown in that link). A 9V supply will work with normal mosfets, but if you can find a "logic level" version, it will be turned on completely with even a lower voltage. Pay particular attention to the fact that the mosfet is connected to ground (your negative) and the load is connected between the positive supply and the mosfet. Also, note that the power supplied by a 9V transistor battery is limited.

John

 

[sub2d]

Hi John,

Thanks again for the info, and the new link. I'll have a good read through that later tonight. I'm still an absolute novice, so I don't really even know what I'd do with more current at the moment. I'm generally just doing "electronics-by-numbers", following guides exactly, without really understanding how it all works, but I hope to pick bits up as I go.

Can you recommend any good, simple projects for me that'd be a good thing to make next? No worries if not. Now that my oscillator's done, I'm not sure what to focus on. I'm most interested in sound-making devices, but I'd happily make anything. I suppose I'm limited by my components - I have bags of resistors, capacitors, diodes, potentiometers, switches, and plenty of 40106 chips - but I don't know what I can actually do with them. I may research trying to make some kind of very basic push button drum machine. Could be fun.

Cheers,
Jamie

 

[ericgibbs]

hi,
Look thru these.
http://fluxmonkey.com/electronoize/40106Oscillator.htm

**broken link removed**

http://www.discovercircuits.com/C/capacitance-sw.htm

**broken link removed**

http://www.electroniq.net/other-projects?page=35

 

[sub2d]

Brilliant, thanks very much. Looking forward to cracking on with the next project! I might launch straight into the 3-oscillator one next. Seems like a logical step.

 

[jpanhalt]

I would also recommend Roman Black's site (Mr. RB here). The projects there might be a little advanced, but they are excellent.

https://www.romanblack.com/

You didn't ask, but I will give you my opinion about analog and digital. I suggest staying with analog circuits for a little bit. Make a flashing LED with an NE555 (or LM555). Make a reaction timer or an rpm meter (tachometer) for a motor. Make a PWM motor controller, like for a model car or robot. Once you are a little comfortable with that, I suggest trying some digital, again starting with a flashing LED.

If you find you like electronics, I would suggest getting a cheap, possibly used, oscilloscope. It will be your first, but probably not your last scope.

Hope to see a lot more from you here.

Regards,

John