Help me with power supply for a VOX circuit

[bbexpress]

help me on power supply

**broken link removed**
for the circuit VOX above, power supply is 12V
but I just have 3V, or 6V maximum. Can it supply that circuit. If not,how come I do it.
thank you.

 

[jzaghal]

Re: help me on power supply

Hi,

I beleive it should work on 6V providing you change the relay to
a 6V type, or even better a 5V type.

Good Luck.

 

[flatulent]

Re: help me on power supply

One critical thing to keep in mind is the input and output range of the op amp. Some cannot go within a few volts of either supply rail. You may be better off using a step up switching supply to power the circuit at 12 V.

 

[bbexpress]

Re: help me on power supply

jzaghal, I'm not sure I can understand how come I change relay to 5V, and it works for circuit. Can you explain more details.
Actually, I just want to use that circuit to activate a small alarm. The power is just 2 AA batteries or 4 AA is maximum. I can not get 8 batteries to supply for voltage.

 

[jzaghal]

Re: help me on power supply

Hi,

Say you want to operate the circuit on 6V dc from four AA batteries.
6V is good enough to power the Op-Amps. But then when the switching
transistor is active it will need to operate a relay rated for 5V or 6V,
and a 12V relay such as the one in the circuit will not operate from
a 6V source.

Hopefully, the gain of the op amps will be enough to amplify the audio
clap signal. If not, you can change the gain of the Op-Amps,
but I do not think you need to do that.

Hope this is clear.

Bye.

 

[Borber]

Re: help me on power supply

If I can suggest, replace diodes D2 and D3 with shotky type. Maybe resistor R8 needs to be decreased to 5.6kohm. Relay for 6V supply version must be rated for 5V operation.

 

[bbexpress]

Re: help me on power supply

Thanks for your help.
But Im still need help for relay.
Is it DRSPST5 from the website https://www.futurlec.com/RelDip.shtml

 

[Borber]

Re: help me on power supply

Selected relay is OK if you need closed contact when relay is activated, otherwice you can use DS2Y-S-DC5V DPDT 5V 2A DIP Relay.

 

[bbexpress]

Re: help me on power supply

Can you let me know what does that mean R8 and C1 of circuit above. Thanks.

 

[Borber]

Re: help me on power supply

R8 is needed for DC supply of electret microphone build in amplifier. It is allso load resistor for amplifier. C1 is filter capacitor for supply voltage. Supply voltage source must have low AC impedance to avoid possible unwanted couplings between amplifiers and thus possible unstabilities of operation.