complete project

[6666]

The vco? I used an old 4046

Hi yes, thats the one.

I'm about to implement my audio modulator that converts DC target response to sinus

Thats interesting news Davor, any more details please, this area does not get much attention.

[Davor]

You can see it from here on http://www.geotech1.com/forums/showt...241#post168241 ... provided you can see pictures on the forum. Some further improvements are in the following posts. There is also a demonstration of this contraption acting as a DSB modulator.
I also started making a PCB layout for a prototype (activity I'm not particularly fond of) and somehow didn't make it yet.

[6666]

Thanks Davor
I will try and look at your post attachments when the forum is running correctly just getting messages saying ERROR 403 - FORBIDDEN

[mickstv]

Hi Tinkerer, here's a present for you "the circuit below". I've just finished it and added it to my PI detector. It should work for the TEM as well.

In my PI the circuit outputs slight threshold level until a target is detected and given the timing I use it produced a higher pitch for fast TC targets, with a volume level increase. Whereas long TC targets produce a lower pitch, with a volume level increase. Also the higher/lower pitch is variable dependent on target type and how close it is to the coil.


This isn't the complete circuit missing, are things like bypass caps and volume control etc.

[6666]

Thanks Mick

[Tinkerer]

Thank you Mick. This looks like a very useful circuit.

We all agree that a good audio can help a lot in making the detecting enjoyable. It is also very important for discerning targets.
I propose we make a joint effort to produce a fully developed circuit and then a small PCB "shield" that can then be added to all sorts of detectors.

For this to work we will need to establish some sort of standard.

Opinions???

[mschmahl]

This sounds good. I think the first standart is that all work with the same elektronic design software for easy interchangeability of datas.
I think DesignSpark is a good one. It is free downloadable with a lot of tools.

[mickstv]

Thanks Mick

Thank you Mick. This looks like a very useful circuit.

We all agree that a good audio can help a lot in making the detecting enjoyable. It is also very important for discerning targets.
I propose we make a joint effort to produce a fully developed circuit and then a small PCB "shield" that can then be added to all sorts of detectors.

For this to work we will need to establish some sort of standard.

Opinions???

No worries 6666 and Tinkerer.

At one stage I was just using the 4046 setup, the same as Tinkerer's circuit, but the biggest problem was the constant tone. With the circuit I'm running now i can set the threshold to be just barely audible until a target is detected. Small targets are easily detected now.

[Tinkerer]

No worries 6666 and Tinkerer.

At one stage I was just using the 4046 setup, the same as Tinkerer's circuit, but the biggest problem was the constant tone. With the circuit I'm running now i can set the threshold to be just barely audible until a target is detected. Small targets are easily detected now.

On my first 4046 circuit I used the enable pin to control the sound. 2 pots, controlled a "noise band" where the audio was switched off. However, I prefer to have a continuous barely audible constant sound, so that one knows that everything is working OK. Also, the dynamic range of my audio was not very perfect, will try to improve that.

On your circuit you have 2 outputs, frequency and volume combined. I like that.

[Tinkerer]

This sounds good. I think the first standart is that all work with the same elektronic design software for easy interchangeability of datas.
I think DesignSpark is a good one. It is free downloadable with a lot of tools.

I fully agree and can only recommend the Designspark software. It is totally free, has developed a whole lot over the last 2 years and is backed by a very powerful worldwide company. By the way, they also offer a 3D mechanical design software now. Also free. I have not tried that one yet.

mschmahl, please tell us about your experience with the TINKERERS SB design. What were the problems? Let's see how we can fix them.

[Davor]

Speaking of some common ground, I also think some audio shield is a very good idea. Instead of creating audio solution for each and every design we make, a common solution(s) is a very good idea.

I for start thought of this very approach for all my future designs. I know, they are not coming out on a conveyor belt as I might wish them to, but eventually I'll come up with some. I concluded that I want a real balanced mixer to create my audio as it fixes several drawbacks of nowadays detectors.
First, real sine-wave is not nearly as tedious to listen to as a common squeaking square-wave (or worse)
Second, there is a huge supply of small/deep targets hiding below the threshold of common detectors, but easily recognised in background chatters - provided those chatters are not annoying
Third, proportional sound enables a detectorist to experience the "immersion", a special feeling of a device being extension of one's own senses.

A good sound shield should have completely linear input DC to output sinus relationship + gating (in case someone insists on applying thresholds). It should also have to be ready to deliver VCO capability. Bonus features could include some phase shifting to enable binaural listening, although it makes sense only if two channels audio is expected.

So a basic shield should be a single audio channel performing balanced audio modulation, with gating and VCO, also some proper power amplifier with volume control.

Maybe we should open a separate topic on this.

[mschmahl]

mschmahl, please tell us about your experience with the TINKERERS SB design. What were the problems? Let's see how we can fix them.

There are 2 problems:
1. I have a very big coil (50 cm diameter). The power for this coil is 12V. If i get the tinkerer SB to start, than i only have a flybackvoltage of 330 V. With 30 V power for the coil the flyback is better (800-850 V) and the depth, too. But it is problematic for the rest of the TX circuitry.
2. If i start the tinkerer SB normal with the switch, than all is working except the TX-coil. The problem seems to be that the TX-cap´s are not loaded enough before the first pulse come from the pic. I got the Tinkerer to run in my videos only with a weird starting procedur. I had connect only Bat. 0V and Bat 12V and later 6V ( hope it was in this order it is some month´s ago). So the tinkerer SB was starting in each fifth try.

[Tinkerer]

There are 2 problems:
1. I have a very big coil (50 cm diameter). The power for this coil is 12V. If i get the tinkerer SB to start, than i only have a flybackvoltage of 330 V. With 30 V power for the coil the flyback is better (800-850 V) and the depth, too. But it is problematic for the rest of the TX circuitry.
2. If i start the tinkerer SB normal with the switch, than all is working except the TX-coil. The problem seems to be that the TX-cap´s are not loaded enough before the first pulse come from the pic. I got the Tinkerer to run in my videos only with a weird starting procedur. I had connect only Bat. 0V and Bat 12V and later 6V ( hope it was in this order it is some month´s ago). So the tinkerer SB was starting in each fifth try.

Could you post the schematics of your setup? We can then use actual part numbers to work on solving the problems.

There are several possible causes that can combine to produce the problems you have.

What is your power supply?
What is your total coil and Mosfet resistance? The total resistance, TC, BU, cable and Mosfet and the cycle frequency, condition the consumption of the TX power.

I believe you have a big coil for searching deep targets. The TX timing is designed for that.
The TX timing together with the flyback capacitor control the Flyback voltage. The Flyback voltage per se is not important, but must never reach close to the Mosfet avalanche voltage.

Are you using a PIC 16F690? We can also use different timing cycles for different coil sizes and target sizes.

[Tinkerer]

Speaking of some common ground, I also think some audio shield is a very good idea. Instead of creating audio solution for each and every design we make, a common solution(s) is a very good idea.

I for start thought of this very approach for all my future designs. I know, they are not coming out on a conveyor belt as I might wish them to, but eventually I'll come up with some. I concluded that I want a real balanced mixer to create my audio as it fixes several drawbacks of nowadays detectors.
First, real sine-wave is not nearly as tedious to listen to as a common squeaking square-wave (or worse)
Second, there is a huge supply of small/deep targets hiding below the threshold of common detectors, but easily recognised in background chatters - provided those chatters are not annoying
Third, proportional sound enables a detectorist to experience the "immersion", a special feeling of a device being extension of one's own senses.

A good sound shield should have completely linear input DC to output sinus relationship + gating (in case someone insists on applying thresholds). It should also have to be ready to deliver VCO capability. Bonus features could include some phase shifting to enable binaural listening, although it makes sense only if two channels audio is expected.

So a basic shield should be a single audio channel performing balanced audio modulation, with gating and VCO, also some proper power amplifier with volume control.

Maybe we should open a separate topic on this.

I agree on the separate topic. Should we use the thread: http://www.geotech1.com/forums/showt...he-Audio/page2
Or would you prefer to start a new thread?

The audio is very important in a metal detector.

[Davor]

That topic is OK, but maybe it will be even better to start a completely new topic with less general notion. Say, we agree on some common ground, name it, and open a topic covering that aspect. For example, "gated proportional audio with VCO". Or, "2 channel proportional audio with optional binaural processing". Or something like that.