Adding LEDs and/or Headphone output to PiratePi

[Astromic]

Hi,
I built this detector called "Pirate" or something, it's a Russian designed PI device, the process was fun and the results are very good, especially after several trials and errors with coil designs it showed amazing potentials compared to it's simplicity.
Now I'm looking for a way to add a LEDs vu meter, or at least just one LED to help in noisy environment. I believe I can use a LM3914 for the vu meter but I don't know how!! I also tried to play with a 2N2222 to trigger the signal right from the buzzer to a single LED also with no luck. And adding a 3.5 plug support for headphone attachment is far beyond my knowledge, as I'm still learning!!
Calling all gurus here for help, and please consider that I'm still learning



Mike

[6666]

just google diy sound level meter schematic, then click images, you will get lots of ideas to try and modify for what you want

[Tim]

Check the LM3914 datasheet. There is a a hookup schematic there. Some external components are needed, and input resistor/pot value will need to be adjusted to not over/under drive the 3914.
Headphone jack is easy enough.
Neg to peizo neg. Pos to phone plug jack that disconnects when pin is inserted and connects to peizo when pulled out.

[gaby_sult]

https://www.youtube.com/watch?v=P37NXEKZjfs

[Tim]

Good link gaby. I think you can also wire it to be a centred metre, for say a ferrous/non-ferrous meter on a VLF. Alternatively 2 separate 3914s, one indicating pos and one neg.

[Tibuck19]

[QUOTE=Astromic;242518]Hi,
I built this detector called "Pirate" or something, it's a Russian designed PI device, the process was fun and the results are very good, especially after several trials and errors with coil designs it showed amazing potentials compared to it's simplicity.
Now I'm looking for a way to add a LEDs vu meter, or at least just one LED to help in noisy environment. I believe I can use a LM3914 for the vu meter but I don't know how!! I also tried to play with a 2N2222 to trigger the signal right from the buzzer to a single LED also with no luck. And adding a 3.5 plug support for headphone attachment is far beyond my knowledge, as I'm still learning!!
Calling all gurus here for help, and please consider that I'm still learning

Maybe you can do what I did, I used a Red and green LED power goes to green which is always on and red goes with the out put of headphone jack, when metal is detecting and sound goes through the headphones, the light changes from yellow( color mixing ) to solid red when the object is closest to the coil.

https://www.youtube.com/watch?v=o--a...ature=youtu.be

[waltr]

If the schematic in the first post of this thread is correct then there is NO DC level indicating Target Detected. Therefore, one can not simply connect a VU meter circuit of an LED to indicate a target.
This is due to the TX pulsing is also the Audio tone generator which then simply gets louder with a target.

I would need to see the output with an O'scope (post scope pictures) without and with target to determine how to do a VU meter or LED.

My guess is a rectifier circuit and amp to produce a DC LEVEL needs to be added.

[Astromic]

Thanks' guys, I really appreciate all your inputs
The headphone addon was quit easy, I just didn't recall that there is a 5 pin 3.5mm socket which turn off speaker(yeah, I have a lousy memory) lol.. As I told you I build it first because I need to learn by practice and for the sake of DIY pleasure we all seek ,, I could use an Oscilloscope to capture the output, well I don't have one right now, but I ordered a portable "poor man's scope" named DSO150, and expecting it to arrive anytime soon, as a starter device to learn on.. please waltr tell me which pin to prob and any advice to get a clear image, as I told you I'm learning and everything you guys suggest I research it thoroughly ..
There is another thing I wish to try, that is a vibration dc motor add on, because I might later built one and waterproof it for underwater detecting!! Can I use a simple npn transistor as a switch to turn the motor on? or there will be the same issue of no dc level to detect?

Mike

[Tibuck19]

Thanks' guys, I really appreciate all your inputs
The headphone addon was quit easy, I just didn't recall that there is a 5 pin 3.5mm socket which turn off speaker(yeah, I have a lousy memory) lol.. As I told you I build it first because I need to learn by practice and for the sake of DIY pleasure we all seek ,, I could use an Oscilloscope to capture the output, well I don't have one right now, but I ordered a portable "poor man's scope" named DSO150, and expecting it to arrive anytime soon, as a starter device to learn on.. please waltr tell me which pin to prob and any advice to get a clear image, as I told you I'm learning and everything you guys suggest I research it thoroughly ..
There is another thing I wish to try, that is a vibration dc motor add on, because I might later built one and waterproof it for underwater detecting!! Can I use a simple npn transistor as a switch to turn the motor on? or there will be the same issue of no dc level to detect?

Mike

Mike , keeping it simple is always the better option, as for a vibrating MD, I used these https://www.ebay.ca/itm/1-5-10-20pcs...ZFPxJO59ybcMdA They are dirt cheap vibrate strongly for there size and they run on less the 3V which means you can wire them right to the speaker connection of the board. you might even need to place a resistor to limit the voltage.

[waltr]

Ok Mike, When you get your scope start with the simpler points like the output of the 555 timer on pin 3.
This will be a pulse train with an amplitude close to the battery Voltage.

Once you can adjust to see this then go check the two outputs of U2.
Post back here findings and questions.

[Astromic]

Out of curiosity till the scope arrives, I built a simple circuit for the LM3915 and attached the audio output to it directly, the results was as expected, all the leds run together in case of signal(metal close to coil) and all turn off also together, no "vu" meter to indicate the strength or a ladder effect.. so I figured that if I took the signal from the audio source, I'm gonna need to measure frequency not voltage of pulses, because the voltage there is steady!! Am I right or missing something here?

Also, if there is an option to capture the signal from the audio source, is there some kind of IC to do the same as LM3915 but only triggers a single LED? I mean there is no need for 10 LEDs if they turn on and off together, right?
well it's just a though to try, until I figure out a way for a proper vu meter!!

Mike

[waltr]

The audio is a fixed frequency, when it detects metal the audio volume increases but frequency stays the same. Right?
The Scope will verify this.

Therefore, you need to rectify and filter.
From the audio go to a diode ->|- then a resistor (~2k) and cap (~470nF) to ground. This should then produce a DC Voltage level that increases when metal is detected. The VU meter chip can then be used. Be sure to set output Voltage level needed by the VU chip's input.
Again, scope will verify rectification and filtering. A Voltmeter can be used to check levels needed.

[homefire]

I'm Lazy. https://www.banggood.com/VU-Meter-Dr...r_warehouse=CN

[Tim]

Take waltr's advice but also read the datasheet for 3914 (at alldatasheet). It is 13 pages from memory, and has extensive information and examples of how to use this chip, including the answer to your question regarding not turning on all LED's at once, by the cascading configuration. However taking waltr's advice LED's should only come on at increased signal strength, depending on your input resistance value.
Not having a scope should only be a minor hindrance to sorting this out.
As stated previously a single LED can be powered from the speaker output. For an example of this see the Baracuda RevD schematic (or many others).

[6666]

I'm Lazy. https://www.banggood.com/VU-Meter-Dr...r_warehouse=CN

And I thought I was slack, might work
guess this is the schematic