Audio Triggered Switch Help

[CBB9]

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

spec

I like better . I have updated the parts list with the addition of those transistors as well as color coded the list to what I have on hand currently (Green I have, Red I need). Would any of the diodes found here work as a replacement for D1/D2? It's looking like I might get lucky and be able to put this together using components from my local electronics store (Radio Shack).

Note: 1N4148 is listed on the site, but is out of stock at my local store. I have a couple 1N4001's on hand if those work?

 

[DerStrom8]

I like better . I have updated the parts list with the addition of those transistors as well as color coded the list to what I have on hand currently (Green I have, Red I need). Would any of the diodes found here work as a replacement for Q2/Q3? It's looking like I might get lucky and be able to put this together using components from my local electronics store (Radio Shack).

Note: 1N4148 is listed on the site, but is out of stock at my local store. I have a couple 1N4001's on hand if those work?

'Q' designates a transistor. Why are you asking if you can replace them with diodes?

Maybe I should read the rest of the thread....

 

[spec]

I like better . I have updated the parts list with the addition of those transistors as well as color coded the list to what I have on hand currently (Green I have, Red I need). Would any of the diodes found here work as a replacement for Q2/Q3? It's looking like I might get lucky and be able to put this together using components from my local electronics store (Radio Shack).

Note: 1N4148 is listed on the site, but is out of stock at my local store. I have a couple 1N4001's on hand if those work?

As DS8 says D is the name rather than Q, but theses diodes would probably be suitable (no specification listed though): https://www.radioshack.com/collections/diodes-rectifiers/products/silicon-switch-diode

spec

 

[CBB9]

DerStrom8 spec - Thanks for catching that, meant D1,D2. I corrected the original post to save future readers the confusion.

 

[spec]

You never see me making mistakes.

spec

 

[CBB9]

You never see me making mistakes.

spec

I completed the circuit using the Darlington, using my iPhone 6s as an audio source playing 14khz at full volume. I see 0.145v between the A13 (in schmeatic) and 0v. Not sure where I went wrong, I tore it all down and rebuilt it twice, also tried an Android device as the audio source which read 0V (device output isnt as strong as the iPhones when using headphones). I used 2x 0.22uF Polyester-Film Capacitors in parallel for C2, could that be causing an issue?

 

[spec]

Hi CBB9,

I completed the circuit using the Darlington, using my iPhone 6s as an audio source playing 14khz at full volume. I see 0.145v between the A13 (in schmeatic) and 0v. Not sure where I went wrong, I tore it all down and rebuilt it twice, also tried an Android device as the audio source which read 0V (device output isnt as strong as the iPhones when using headphones). I used 2x 0.22uF Polyester-Film Capacitors in parallel for C2, could that be causing an issue?

To test the circuit of post #23, A13 should be connected to 12V via a 1K resistor to simulate the starting circuit in your automobile.

Other voltages and resistors can be used to simulate your automobile start circuit according to the formula V/R= 0.012A, where V is in Volts and R is in Ohms. The voltage should be in the range 6V to 20V. The values of both voltage and resistance are not critical.

Two 0.22 polyester film capacitors in parallel will be fine.

By the way, have you noticed in the ERRATA that there have been some value changes to the circuit of post #23

spec

 

[CBB9]

Hi CBB9,



To test the circuit of post #23, A13 should be connected to 12V via a 1K resistor to simulate the starting circuit in your automobile.

Other voltages and resistors can be used to simulate your automobile start circuit according to the formula V/R= 0.012A, where V is in Volts and R is in Ohms. The voltage should be in the range 6V to 20V. The values of both voltage and resistance are not critical.

Two 0.22 polyester film capacitors in parallel will be fine.

By the way, have you noticed in the ERRATA that there have been some value changes to the circuit of post #23

spec

I missed the ERRATA. I have rebuilt the circuit with those changes and I'm almost there. With audio on I'm now seeing the proper voltage, but 0.00A (something lower than my multimeter can read), not enough to trigger the A13 signal.

 

[spec]

I missed the ERRATA. I have rebuilt the circuit with those changes and I'm almost there. With audio on I'm now seeing the proper voltage, but 0.00A (something lower than my multimeter can read), not enough to trigger the A13 signal.

I suspect that there is not sufficient voltage from the audio. The audio input threshold to make the Darlington transistor conduct is (4 * 0.6V) = 2.4V peak to peak or (4* 0.6V)/ (1.414 * 2) = 0.849V (849mV).

How are you generating the 14KHz?

spec

By the way, connect your multimeter, set to the volts range, to A13 (other lead to 0V). If the multimeter reads 12V, A13 is not asserted. If the multimeter reads 1.2V, or less, A13 is asserted.

 

[spec]

Just to give some confidence that the voltage doubling rectifier works, below is a simulation of the voltage doubling rectifier with a 14KHz, 6V peak to peak input (2.12V RMS), first with standard silicon diodes and then with Schottky diodes (more voltage output).

spec

 

[CBB9]

I suspect that there is not sufficient voltage from the audio. The audio input threshold to make the Darlington transistor conduct is (4 * 0.6V) = 2.4V peak to peak or (4* 0.6V)/ (1.414 * 2) = 0.849V (849mV).

How are you generating the 14KHz?

spec

By the way, connect your multimeter, set to the volts range, to A13 (other lead to 0V). If the multimeter reads 12V, A13 is not asserted. If the multimeter reads 1.2V, or less, A13 is asserted.

I've tried an audio sample from YouTube, and a Tone Generator for Android. Both succeed in showing a perfect 12.0V when audio is on. Lowering the frequency lowers the voltage seen on the multimeter. When testing the power supply provides 12.38V, so a 0.36V drop?

Car battery sits at 12.2V, A13 to 0V reads 11.4V

Measuring the AC voltage of the headphone output I get 0.3V

 

[spec]

I've tried an audio sample from YouTube, and a Tone Generator for Android. Both succeed in showing a perfect 12.0V when audio is on. Lowering the frequency lowers the voltage seen on the multimeter. When testing the power supply provides 12.38V, so a 0.36V drop?

Car battery sits at 12.2V, A13 to 0V reads 11.4V

Measuring the AC voltage of the headphone output I get 0.3V

Ah, 0.3V (RMS) = (2 * 1.414) * 0.3V = 0.848V peak to peak which is not enough voltage to overcome the forward voltage drop of the two silicon diodes and the two VBEs of the Darlington transistor (0.6V * 4). Mind you, your multimeter may be under-reading at 14KHz.

I will give all this some thought and get back.

spec

 

[CBB9]

Ah, 0.3V (RMS) = (2 * 1.414) * 0.3V = 0.848V peak to peak which is not enough voltage to overcome the forward voltage drop of the two silicon diodes and the two VBEs of the Darlington transistor (0.6V * 4). Mind you, your multimeter may be under-reading at 14KHz.

I will give all this some thought and get back.

spec

Would using the BAT43's and the AO3414 solve the voltage drop?

 

[spec]

POST Issue 06 of 2017_02_02

Hi CBB9,

Below is the schematic for Version 2 of the Start Command Circuit which should do the job.

spec

ERRATA
(1) Connect a 100K resistor across C3

​

NOTES
(1) Hopefully, this is a practical circuit and will produce a /START COMMAND of around 0.2V.
(2) The circuit still does not use the 12V power rail.
(3) R8 is notional and will need to be adjusted for satisfactory operation. Increasing the value of R8 will decrease the sensitivity.
(4) Schottky diodes are not required
(5) A MOSFET is not required.
(6) R9 is for testing only
(7) In case anyone is wondering, the transformer is shown connected the correct way around (input to secondary)
(8) The transformer is not optimum but is a RadioShack type.
(9) The input and output are totally isolated, which is a good thing.


LINKS
(1) https://www.radioshack.com/products/radioshack-audio-output-transformer

 

[spec]

Would using the BAT43's and the AO3414 solve the voltage drop?

No afraid not. A modified circuit would be required as post #54 above.

spec

 

[CBB9]

POST Issue 05 of 2017_02_02

Hi CBB9,

Below is the schematic for Version 2 of the Start Command Circuit which should do the job.

spec

View attachment 104007​

ERRATA
(1) Connect a 100K resistor across C3

​

NOTES
(1) Hopefully, this is a practical circuit and will produce a /START COMMAND of around 0.2V.
(2) The circuit still does not use the 12V power rail.
(3) R8 is notional and will need to be adjusted for satisfactory operation. Increasing the value of R8 will decrease the sensitivity.
(4) Schottky diodes are not required
(5) A MOSFET is not required.
(6) R9 is for testing only
(7) In case anyone is wondering, the transformer is shown connected the correct way around (input to secondary)
(8) The transformer is not optimum but is a RadioShack type.
(9) The input and output are totally isolated, which is a good thing.
(10) C3 value is not critical (0.2uF will be fine)


LINKS
(1) https://www.radioshack.com/products/radioshack-audio-output-transformer

You Rock! I'll try to get to Radio Shack tomorrow night. For note #1, is that supposed to be 0.2A?

Baby boy due any day now, so if I disappear for a bit you know why!

 

[CBB9]

In the meantime I just completed this circuit with what I had on hand. It's not ideal as it relies on a power supply, but it does meet the need for those who don't care. I used a 2N3904 in place of the BC547.

 

[spec]

You Rock! I'll try to get to Radio Shack tomorrow night. For note #1, is that supposed to be 0.2A?

Baby boy due any day now, so if I disappear for a bit you know why!

Hope all goes well with the new miniature CBB9.

No, note #(1) in post #54 is correct. The engine /start command is a switch to 0V and when made the switch will be conducting 0.01A as stated in your post #7

Q1 in the circuit of post #54 acts as a switch but when it turns on, by current flowing into its base, it will have 0.2V between its emitter and collector, unlike a true switch or NMOSFET, which will, essentially, have 0V across them when switched on.

The, 0.2V is just a characteristic of the 2N2222 BJT. It would be higher for a BC546/7/8/9.

I would not think that the engine management system will be concerned about the odd 0.2V and should still recognize that as a valid '/START ' command (/ means not or low voltage)

spec

 

[spec]

spec - I do. At 10A the current is .01

Just to confirm: You used a digital multimeter switched to the 10A range and the digital display read 0.01 (10mA).

Is that correct?

spec

 

[CBB9]

Just to confirm: You used a digital multimeter switched to the 10A range and the digital display read 0.01 (10mA).

Is that correct?

spec

Correct. I will supply an image as soon as I have a chance to validate I am not crazy!