Audio Triggered Switch Help

Status
Not open for further replies.
spec said:
Q2=2N3904, Q3=2N2222 would be best. In fact for Q3 the 2N2222 is probably better than BC54x

spec
Click to expand...

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?
 
Last edited:

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

Maybe I should read the rest of the thread....
 
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
 
Last edited:
spec said:
You never see me making mistakes.

spec
Click to expand...

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?
 
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
 
Last edited:

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.
 
CBB9 said:
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.
Click to expand...
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.
 
Last edited:
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




​
 
Last edited:

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
 
Last edited:

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?
 
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
 
Last edited:

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!
 
Last edited:
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.
 
CBB9 said:
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!
Click to expand...

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
 
Last edited:
spec said:
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
Click to expand...

Correct. I will supply an image as soon as I have a chance to validate I am not crazy!
 
Status
Not open for further replies.

Similar threads

S
  • Question
audio input line problem
Replies
16
Views
2K
SentinelAeon
S
C
  • Question
Machine in shed for 15yrs - 1/4" audio tape PR99 Revox
2
Replies
20
Views
3K
Tony Stewart
M
  • Question
Audio activated LEDs
Replies
14
Views
4K
Tony Stewart
K
  • Question
Help identifying a switch! Noob here!
Replies
4
Views
949
kippy88
K
C
  • Question
relay and diode
Replies
10
Views
2K
chrisjw24
C
Menu
Log in
Register
Cookies are required to use this site. You must accept them to continue using the site. Learn more…