Audio switch activated by a clap

[grexbeast]

Hi guys, I've found a design online for a simple clap activated switch however not everything is going as I really want it.

Here is the design
http://www.buildcircuit.com/CLAP-SWITCH/

The output is too low, I've tried removing R4 there was more power but the system lost control and turned on and off on it's own. I've also put a trimmer (0 - 10kOhms) in the place of R5 so I could decrease it's value and increase the sensitivity of the mic which worked fine up until I've also put a trimmer instead of R4 and tried adjusting that then it just fried everything. Please can anyone help me here I would really like for this to work and give more power instead of almost a 1/4 on the output out of what the batteries are giving on the input. I get it that it's made for an LED but can't I just add or take out something to make it work with say a regular toy motor?

[pebe]

Your problem is you have no DC connection to pin2 of the 555, so the pin 'floats'. A 555 triggers when pin2 goes below 1/3 of the supply voltage (so 2V in your case)

So connect a 10K resistor between pin2 and +6V, and another 10K between pin2 and 0V. That will put +3V on the pin, and it will trigger with a 1V negative pulse from C2. If you want to make the sensitivity adjustable, fit a 50k pot instead of the two resistors, with the wiper connected to pin2.

A 555 can supply 200mA to a load. If you need more than that, you will need a driver transistor.

[grexbeast]

Wow, thank you! I will try this and write back how it works =)

[grexbeast]

I've tried the 10k resistor advice, no change, it used to react to whistles now it reacts only to strong claps close by but I don't think it has anything to do with the add on. Instead of 10kohm resistors I connected trimmers which I first set at 10kohm value and varied their values later to see changes. It seems that the sensitivity really is controlled that way but I still couldn't make it work while I'm further away from the microphone. I will try tomorrow with a 50k potentiometer with 3 connections. I forgot to mention the real problem with the circuit. It works even without the 10kohm resistors added but it kind of shuts down after 10-15 minutes where claps don't turn it on again. Then it starts again after you bang it really hard, but if you leave it in idle again 10-15 minutes again it won't react which is really frustrating because it's sole purpose is to wait for you to clap. PLESE HELP! I'm really out of ideas on how to make it more sensitive and make it work longer than 10 minutes at a time.

Here are some pictures

http://imageshack.com/a/img905/4548/XTzsDY.jpg
http://imageshack.com/a/img907/2347/gSasUT.jpg
http://imageshack.com/a/img910/1617/XvV2zY.jpg
http://imageshack.com/a/img910/9710/KfD6Uf.jpg
http://imageshack.com/a/img905/7880/OpxV8h.jpg

[grexbeast]

I've been connecting and disconnecting the 10kohm trimmers and now the circuit is no longer activated by a clap but only if I touch the + or + wire with my finger! It functions like a touch switch!? Can anyone explain? I don't need a touch switch, I would really like a working sound switch, doesn't even have to be a clap. If anyone has a working schematic I would be even willing to make a completely different circuit just so it finally works. Also if anyone has any suggestions how to make this circuit work, please help.

[Relayer]

Hello grexbeast,
Going by the pictures you've posted up on Imageshack, it looks like Pin 3 of the 555 IC is wired to a resistor that joins to what? A small speaker?
Pin 2 is supposed to have a coupling capacitor connecting it to the collector of Q2, to which you have, but you have the trimpot connected to the wrong side of the capacitor in question. By this configuration the capacitor isn't able to block any DC entering Pin 2, thus could be the reason it now works as a touch switch instead.
I'll post up a wiring diagram for you, in the hopes it helps getting your circuit to work.
Regards,
Relayer

[grexbeast]

Thanks Relayer. Yes, it's a small speaker, I use it as a substitute for a toy motor at the moment. One trimmer burned up just now. The upper one connected to the positive lead. Can I somehow connect a relay instead of an LED, so that I can use that as a switch for the speaker? Thanks for your help, I hope your diagram will finally help solve this.

[Relayer]

Thanks Relayer

You're welcome

Check the link below for the wiring diagram:

http://i.imgur.com/CQgxQm7.jpg

Unfortunately the way I located the components, both transistors MUST be viewed from their bottoms. Therefore, when you're doing the wiring, make sure you have the transistors bottoms facing up. Its way too easy to make a mistake. I've buggered up plenty of times in the past. lol
I'll make up a supplement to the wiring diagram to which you can install a relay instead of using an LED.
By the way, if you're still encountering problems even after following my diagram, then there is a possibility the 555 Timer IC may be damaged. Especially if you burned out a trimmer.
Please let me know how you get on. In the meantime I'll get busy with the supplement.
Regards,
Relayer

[Relayer]

OK, supplement done.
Click link below:

http://i.imgur.com/RWiu1Jk.jpg

The relay you'll be able to get from Jaycar, the code is: SY-4058.
Once again, ALL the transistors are shown with their bottoms facing upwards.
Also, you are not restricted to using a 6 volt supply. The circuit can easily handle 9 or 12 volts. You may have to increase the value of R5 from 4k7 to 10k, and you'll need to get a 9 volt or 12 volt relay to suit, but the rest of the circuit will be fine. No further changes would be needed.
Jaycar has a reasonable range of 12 volt relays, but unfortunately no 9 volt units. Though 9 volts should be able to work the 12 volt relays with minimal chatter, but worst case, a 9.1V zener in series with a 1k resistor between the Collector and Emitter of Q3 would remedy this.
Once again, please let me know how you get on.
Good luck!!!
Regards,
Relayer

[pebe]

Relayer,
Your diagrams still show no DC connection to 555 pin2. At best, the performance will be erratic.

grexbeast,
You only need one pot. How have you wired up the two that your pics show?
As a safety measure, I think you need a switch to disconnect the batteries while you are changing the wiring!

[Relayer]

Relayer,
Your diagrams still show no DC connection to 555 pin2. At best, the performance will be erratic.

Hey pebe,
Pin 2 is not supposed to be tied to DC, hence the coupling capacitor.
If Pin 2 is supposed to be tied to Pin 5, as it seems in the schematic, then Pin 3 should be tied to the 6 volt rail.

I've created the circuit using my breadboard and it works fine. Though R5 can be reduced to a 3k9 or a 3k3 resistor instead of 4k7, as this will increase the sensitivity, though it has to be experimental, as lowering the resistance too much makes it way too sensitive to any noises.
I hope the above helps.
Regards,
Relayer

[pebe]

Pin 2 is not supposed to be tied to DC, hence the coupling capacitor.
If Pin 2 is supposed to be tied to Pin 5, as it seems in the schematic, then Pin 3 should be tied to the 6 volt rail.

Not so. Read the 555 data sheet!

Pin2 is the trigger pin and feeds the base of a bipolar transistor that draws just under 1uA. With no DC path, where would that current come from? The data sheet states that the trigger voltage is 1/3 of supply voltage, so pin2 must be fed with a finite voltage.

Pin2 in not supposed to be connected to pin5. Pin5 connects to a fixed potential divider within the chip, and provides the reference voltages for the two comparitors that comprise the 555. The impedance at that point is less than 4000ohms and I have never found the need for a decoupling capacitor there.

If you connect pin3 (the output) to the 6V rail, then when the output switches the timer will surely pop!

[Relayer]

Pin2 is the trigger pin and feeds the base of a bipolar transistor that draws just under 1uA. With no DC path, where would that current come from? The data sheet states that the trigger voltage is 1/3 of supply voltage, so pin2 must be fed with a finite voltage.

Audio, such as a clap, going into the microphone, amplified by Q1 and Q2 is sufficient to trigger Pin 2.
Pin 2 does not require a constant voltage on it, it only needs to be initialized with a pulse, hence it gets triggered, regardless of a square, saw-tooth, audio etc. used to initiate the sequence.
Touch Plate Controllers work in the same way.

Pin2 in not supposed to be connected to pin5. Pin5 connects to a fixed potential divider within the chip, and provides the reference voltages for the two comparitors that comprise the 555. The impedance at that point is less than 4000ohms and I have never found the need for a decoupling capacitor there.

If you connect pin3 (the output) to the 6V rail, then when the output switches the timer will surely pop!

I agree, I was wondering where you were wanting the DC from for Pin 2. I was only assuming.
Regards,
Relayer

[pebe]

I doubt that you will read the data sheet to understand how it works, so there is nothing further I can add.

[Relayer]

I doubt that you will read the data sheet to understand how it works, so there is nothing further I can add.

Yes, I have read the datasheet.
I guess you didn't see that I wrote that I got the circuit working. The LED does turn on via a loud clap or any loud noise, though for only around 4 seconds.
If I add a 10k resistor between pin 2 and the 6 volt rail, the LED remains on for longer, around 6 seconds.
I have to agree that inserting a 10k resistor between Pin 2 and the 6 volt rail would make it more stable, thus triggering it more reliably, but regardless whether or not the resistor is in circuit, it still gets triggered.
Regards,
Relayer