Audio Triggered Switch Help

[spec]

spec - Having spent many years competing in car audio competition I can attest to all the random goings! With that said, I'm somewhat curious to find out. I like to tinker and test and I'm opening to trying it unfiltered as well as filtered.

I have the circuit now, but just doing the final knockings- it is pretty simple and does not require a power supply so 12V filtering does not enter the equation.

But, if you would like to do some experiments/tinkering you have come to the right website- we are pretty much all experimenters/tinkers on ETO.

spec

 

[CBB9]

I have the circuit now, but just doing the final knockings- it is pretty simple and does not require a power supply so 12V filtering does not enter the equation.

But, if you would like to do some experiments/tinkering you have come to the right website- we are pretty much all experimenters/tinkers on ETO.

spec

You are the man! I didn't think that would be possible with such a low powered audio device. This solution just keeps getting better and better. I'm excited to put it all together.

 

[spec]

POST #34 Issue 12 of 2017_01_31

You are the man! I didn't think that would be possible with such a low powered audio device. This solution just keeps getting better and better. I'm excited to put it all together.

Hi CBB9,

Below is the suggested circuit. I hope it lives up to your expectations.

spec

​

ERRATA
(1) Change R1 to 47 Ohms
(2) Change Q3 to 2N2222 or PN2222 (same chip)
(3) For the Darlington transistor version only, change R3 from 220 Ohms to 4.7K Ohms
(4) Note that C2 (470nF) is 0.47 micro Farads and C1 (2n2F) is 0.0022 micro Farads
(5) Note that R6 (4R7) is 4.7 Ohms
(6) Change C1 to 22nF

VENDORS
(1) **broken link removed**
(2) https://www.digikey.co.uk/product-d...emiconductor-inc/AO3414/785-1009-1-ND/1855951

DATASHEETS

 

[alec_t]

Coupla points. The input to this circuit will be from a headphone jack, so (a) will be 14kHz, not 100kHz and (b) may need amplification to switch Q1 reliably (even though the AO6408 has a turn on threshold of 1V).

 

[CBB9]

Hi CDD9,

Below is the suggested circuit. I hope it lives up to your expectations.

spec

**broken link removed**​

Thank you very much for putting that together! I never would have thought it could be so simple especially without a power supply. Are there any equivalent components that could be used for the diodes and MOSFET? I'm itching to build this today from what I can find locally, a quick online search doesnt turn either of those up at my local Radio Shack. I only see this MOSFET on their website.

 

[spec]

Coupla points. The input to this circuit will be from a headphone jack, so (a) will be 14kHz, not 100kHz and (b) may need amplification to switch Q1 reliably (even though the AO6408 has a turn on threshold of 1V).

Wow, you are quick off the mark Alec.

100KHz signal title changed to 14KHz in post #23, as stated in post #1. Not sure where I got 100KHz from.

You do not want the engine start command threshold voltage to be too low. At the moment the highest worst-case voltage threshold in 566mV RMS, which should be fine, although I am not sure how many headphone jacks on consumer audio equipment will output a frequency as high as 14Khz.

spec

 

[spec]

Thank you very much for putting that together! I never would have thought it could be so simple especially without a power supply. Are there any equivalent components that could be used for the diodes and MOSFET? I'm itching to build this today from what I can find locally, a quick online search doesnt turn either of those up at my local Radio Shack. I only see this MOSFET on their website.

No probs CBB9,

You can use pretty much any small signal diode in place of the BAT43: 1N4148, 1N914, 1N916 etc, but the input drive threshold voltage will go up by (600mV/2) * 0.707V RMS

Afraid the Radio Shack NMOSFET type IRF510 will not be suitable. The type of NMOSFET is central to the design of the 'Engine Start Command' circuit.

But you could try replacing the NMOSFET with a Darlington transistor made from two small signal NBJTs (NPN normal transistors): BC546/7/8/9, BC107/8/9, BC182/3/4 and so on. This would increase the input threshold by (200mV/2) * 0.707 V RMS. UPDATE: Darlington now shown on schematic of post #23.

The Darlington transistor would also have around 1V across it when turned on; the NMOSFET by comparison would have around zero volts across it when turned on.

spec

 

[Les Jones]

Hi spec,
I think there is an error in the schematic that you posted in post #23. I think the positive side of D2 should go to the negative side of D1. As it is C2 will charge during the first few cycles of the input waveform so the positive peak of the waveform at the negative end of D1 is only a little above zero volts.

Les.

 

[spec]

Hi spec,
I think there is an error in the schematic that you posted in post #23. I think the positive side of D2 should go to the negative side of D1. As it is C2 will charge during the first few cycles of the input waveform so the positive peak of the waveform is only a little above zero volts.

Les.

Thanks Les,

I am glad you are around to check my stuff. I blame a late night yesterday- jazz at Bristol and didn't get home until 2:15am. I have just checked the sketch I did yesterday and the diodes are connected correctly.

spec

 

[cowboybob]

Just an observation that crossed my mind.

What are the implications of this scenario:

1. Audio signal for engine start. A13 goes to ground. Engine starts.
2. Vehicle put into Drive.
3. While driving, a second audio signal initiated. A13 goes to ground.

Does (or can) the engine turn off?

 

[CBB9]

Just an observation that crossed my mind.

What are the implications of this scenario:

1. Audio signal for engine start. A13 goes to ground. Engine starts.
2. Vehicle put into Drive.
3. While driving, a second audio signal initiated. A13 goes to ground.

Does (or can) the engine turn off?

It does not turn off, in order to put the vehicle into any gear the key must be placed in the ignition and in the running position. Putting the vehicle into gear without the key in position will turn off the ignition/engine. Sending another pulse or disconnect when in gear appears to have no effect (as expected).

 

[cowboybob]

It does not turn off, in order to put the vehicle into any gear the key must be placed in the ignition and in the running position. Putting the vehicle into gear without the key in position will turn off the ignition/engine. Sending another pulse or disconnect when in gear appears to have no effect (as expected).

I thought as much (right after I posted... ).

 

[CBB9]

No probs CBB9,

You can use pretty much any small signal diode in place of the BAT43: 1N4148, 1N914, 1N916 etc, but the input drive threshold voltage will go up by (600mV/2) * 0.707V RMS

Afraid the Radio Shack NMOSFET type IRF510 will not be suitable. The type of NMOSFET is central to the design of the 'Engine Start Command' circuit.

But you could try replacing the NMOSFET with a Darlington transistor made from two small signal NBJTs (NPN normal transistors): BC546/7/8/9, BC107/8/9, BC182/3/4 and so on. This would increase the input threshold by (200mV/2) * 0.707 V RMS. UPDATE: Darlington now shown on schematic of post #23.

The Darlington transistor would also have around 1V across it when turned on; the NMOSFET by comparison would have around zero volts across it when turned on.

spec

I'll be heading over to Radio Shack in the next few hours to see what I can come up with. I will admit I'm out of my league figuring out alternative components as well as calculating everything. I just realized that you are in the UK and that Radio Shack doesn't exist in your neck of the woods! They have a little 4x4x5 cube with about 64 trays of various components, the most common ones to be used. Here is the link to their online site: https://www.radioshack.com/collections/parts-drawer

 

[spec]

I'll be heading over to Radio Shack in the next few hours to see what I can come up with. I will admit I'm out of my league figuring out alternative components as well as calculating everything. I just realized that you are in the UK and that Radio Shack doesn't exist in your neck of the woods! They have a little 4x4x5 cube with about 64 trays of various components, the most common ones to be used. Here is the link to their online site: https://www.radioshack.com/collections/parts-drawer

The most important parameter of the NMOSFET for your application is a gate threshold voltage (also called gate cut off voltage depending on manufacturer) of 1V or less.

If I remember correctly, we used to have Radio Shack (or were they Tandy) shops in the UK in the 1970s and 1980s. We do still have Maplin electronics shops though but, theses days, most components are bought over the net.

spec

 

[CBB9]

The most important parameter of the NMOSFET for your application is a gate threshold voltage (also called gate cut off voltage depending on manufacturer) of 1V or less.

If I remember correctly, we used to have Radio Shack shops in the UK in the 1970s and 1980s. We do still have Maplin electronics shops though but, theses days, most components are bought over the net.

spec

That's what I figured would end up being the case. I'll put in order in tonight so that I can build out the circuit you provided me, as I see it being the perfect solution not needing an external power source. In the meantime I'm wondering if I could use clap circuit with a 555 to tinker with something today? Something like this. I know my local Radio Shack carries the needed components to build that out, but I don't want to use it as my final solution.

 

[spec]

That's what I figured would end up being the case. I'll put in order in tonight so that I can build out the circuit you provided me, as I see it being the perfect solution not needing an external power source. In the meantime I'm wondering if I could use clap circuit with a 555 to tinker with something today? Something like this. I know my local Radio Shack carries the needed components to build that out, but I don't want to use it as my final solution.

Why not experiment.

spec

 

[CBB9]

No probs CBB9,

You can use pretty much any small signal diode in place of the BAT43: 1N4148, 1N914, 1N916 etc, but the input drive threshold voltage will go up by (600mV/2) * 0.707V RMS

Afraid the Radio Shack NMOSFET type IRF510 will not be suitable. The type of NMOSFET is central to the design of the 'Engine Start Command' circuit.

But you could try replacing the NMOSFET with a Darlington transistor made from two small signal NBJTs (NPN normal transistors): BC546/7/8/9, BC107/8/9, BC182/3/4 and so on. This would increase the input threshold by (200mV/2) * 0.707 V RMS. UPDATE: Darlington now shown on schematic of post #23.

The Darlington transistor would also have around 1V across it when turned on; the NMOSFET by comparison would have around zero volts across it when turned on.

spec

I grabbed 3in1 pack of transistors for the Darlington transistor. The pack contains 5x of 2N2222, 2N4401, and 2N3904. From what I can gather online any of the three should work as a replacement for for a BC546/7. Could you suggest which one is best for this circuit (that is if they will even work)? I went with the 2N3904 for now but need to grab some other components before I can complete the circuit.

 

[CBB9]

POST #34 Issue 8 of 2017_01_29


Hi CBB9,

Below is the suggested circuit. I hope it lives up to your expectations.

spec

View attachment 103907
​

ERRATA

VENDORS
(1) **broken link removed**
(2) https://www.digikey.co.uk/product-d...emiconductor-inc/AO3414/785-1009-1-ND/1855951

DATASHEETS

Does this look accurate? I could't find R5 on the schematic. Is there other equivalent components that could be used for D1/D2 and Q2/Q3?

Parts List:

R1 - 1k-ohm
R2 - 100k-ohm
R3 - 220ohm
R4 - 22k-ohm
R6 - 4.7ohm
C1 - 2.2nF (2200pF)
C2 - 470nF (.47uF)
D1 - BAT43 [OR] 1N4148 [OR] 1N914 [OR] 1N916 [OR] ?
D2 - BAT43 [OR] 1N4148 [OR] 1N914 [OR] 1N916 [OR] ?
Q1 (Option 1) - AO3414
Q2 (Option 2) - 2N3904 [OR] BC546/7/8/9 [OR] BC107/8/9 [OR] BC182/3/4
Q3 (Option 2) - 2N2222 [OR] BC546/7/8/9 [OR] BC107/8/9 [OR] BC182/3/4

 

[spec]

I grabbed 3in1 pack of transistors for the Darlington transistor. The pack contains 5x of 2N2222, 2N4401, and 2N3904. From what I can gather online any of the three should work as a replacement for for a BC546/7. Could you suggest which one is best for this circuit (that is if they will even work)? I went with the 2N3904 for now but need to grab some other components before I can complete the circuit.

Q2=2N3904, Q3=2N2222 would be best. In fact for Q3 the 2N2222 is probably better than BC54x

spec

 

[spec]

Does this look accurate? I could't find R5 on the schematic. Is there other equivalent components that could be used for D1/D2 and Q2/Q3?

Parts List:

R1 - 1k-ohm
R2 - 100k-ohm
R3 - 220ohm
R4 - 22k-ohm
R5 - ?
R6 - 4.7ohm
C1 - 2.2nF (2200pF)
C2 - 470nF (.47uF)
D1 - BAT43 [OR] 1N4148 [OR] 1N914 [OR] 1N916 [OR] ?
D2 - BAT43 [OR] 1N4148 [OR] 1N914 [OR] 1N916 [OR] ?
Q1 (Opt1) - AO3414
Q2 (Opt2) - BC546/7/8/9 [OR] BC107/8/9 [OR] BC182/3/4 [OR] ?
Q3 (Opt2) - BC546/7/8/9 [OR] BC107/8/9 [OR] BC182/3/4 [OR] ?

Yes, that is fine. There is no R5- blame EAGLE

spec