complete project

[Davor]

Actually it is more of a step voltage than a TEM, but does the same job, and step is more PI like. Call it as you wish, but we have finally something new on the block.

My suggestions would be to reconsider the level of filtration throughout system. You have incredible number of filtering stages, and you know about "too much of the good stuff". For starters I'd remove C33 because of the changing impedance of that particular circuit. Then I'd continue removing R14, C26 and R45 (offset is fixed elsewhere already).

My focus recently is on the differential inputs, such as yours. Nice job

[Tinkerer]

Thanks Tinkerer, I'll change my timing tomorrow and have another go.

I think R1 on the TX schematic is incorrect, I would have thought that it would be connecting to ground, like in some of your earlier schematics.



Cheers
Mick

Thanks for the observation. You are correct, R1 should go to 0V or can be omitted.

Tinkerer

[Midas]

Either I'm getting too tired or I'm missing something here.

My understanding is a standard PI would be FET on for say 100us then off again for say 300us then back on again.

Whereas my understanding which is opposite to what your saying is that the FET in the TEM should switch on for 7us then switch off for 97us.

Or am I getting really mixed up.


Cheers
Mick

You should play with Aziz's simulation Mick. Not sure exactly where it is anymore... Anyway here's a picture of what the mosfet gate is doing with respect to coil current:

[mickstv]

You understand right. The TX is ON for 97us and OFF for 7us. That means it is ON almost all the time.
This is a totally new and different Pulse Induction technology. It uses a high power TX pulse while consuming little power out of the battery, due to it's resonant component.

Tinkerer

Thanks Tinkerer, I'll change my timing tomorrow and have another go.

I think R1 on the TX schematic is incorrect, I would have thought that it would be connecting to ground, like in some of your earlier schematics.



Cheers
Mick

[Tinkerer]

Either I'm getting too tired or I'm missing something here.

My understanding is a standard PI would be FET on for say 100us then off again for say 300us then back on again.

Whereas my understanding which is opposite to what your saying is that the FET in the TEM should switch on for 7us then switch off for 97us.

Or am I getting really mixed up.


Cheers
Mick

You understand right. The TX is ON for 97us and OFF for 7us. That means it is ON almost all the time.
This is a totally new and different Pulse Induction technology. It uses a high power TX pulse while consuming little power out of the battery, due to it's resonant component.

Tinkerer

[mickstv]

The pictures are only meant to show the wave shape. For example, the current picture shows a 12A pulse, while the TINKERERS_SB uses only 4A.

I have a HEX file ready, I just want to test run it first before posting.

The Mosfet driver expects a pulse that is ON for about 97us and OFF for 7us, for a total cycle of 104us or about 10k PRR. This is when using a 300uH coil and a 4.7nF capacitor.
You should then get a Flyback of about 550V.

This is the INVERSE of a traditional PI, where the TX is ON for a short time and OFF for a long time.

If you use a traditional PI pulse timing, the coil will ring and the Mosfet will get hot and might self destroy.

Tinkerer

Either I'm getting too tired or I'm missing something here.

My understanding is a standard PI would be FET on for say 100us then off again for say 300us then back on again.

Whereas my understanding which is opposite to what your saying is that the FET in the TEM should switch on for 7us then switch off for 97us.

Or am I getting really mixed up.


Cheers
Mick

[Tinkerer]

Thanks for posting the pictures.

No you haven't posted the HEX file. I was of the understanding that the TEM was driven with a standard TX pulse so I used one of my pic's.

I can't post a Picture at the moment due to a issue my end, but to try and explain it, it just looked like an undampened/ringing waveform. Like a standard PI without the damping resistor fitted. I've obviously done something wrong.


In the pictures what wast he TX on period ?


Mick

The pictures are only meant to show the wave shape. For example, the current picture shows a 12A pulse, while the TINKERERS_SB uses only 4A.

I have a HEX file ready, I just want to test run it first before posting.

The Mosfet driver expects a pulse that is ON for about 97us and OFF for 7us, for a total cycle of 104us or about 10k PRR. This is when using a 300uH coil and a 4.7nF capacitor.
You should then get a Flyback of about 550V.

This is the INVERSE of a traditional PI, where the TX is ON for a short time and OFF for a long time.

If you use a traditional PI pulse timing, the coil will ring and the Mosfet will get hot and might self destroy.

Tinkerer

[mickstv]

There are several mistakes that can cause ringing. If you show me a CRO shot, I might be able to tell you where the problem lies.

Also, did I post the Hex file for the TINKERERS_SB_NM?

Attached is a picture of a TX voltage pulse and a TX current pulse. This is what the wave forms should approximately look like.

Careful with the current measurement, not to damage the CRO. I use a 100mOhm resistor in series with the drain coil wire. A smaller resistor is even better.

Tinkerer

Now, that is funny, I can not add any attachments. I will send this off and try with a different browser.

Thanks for posting the pictures.

No you haven't posted the HEX file. I was of the understanding that the TEM was driven with a standard TX pulse so I used one of my pic's.

I can't post a Picture at the moment due to a issue my end, but to try and explain it, it just looked like an undampened/ringing waveform. Like a standard PI without the damping resistor fitted. I've obviously done something wrong.


In the pictures what wast he TX on period ?


Mick

[Tinkerer]

TX CRO pictures

OK, the attachments seem to work again. Must have been just a quirk of the internet.


Tinkerer

[Tinkerer]

Hi Tinkerer, any chance you could post up a CRO shot of one TX pulse of the output, so that I can see what is expected to be seen. Maybe the CRO shot could be done via a second coil not in null ?

I roughed up a basic TX today and all I got was a over heated FET with lots of ringing. Maybe I did something wrong.




Cheers
Mick

There are several mistakes that can cause ringing. If you show me a CRO shot, I might be able to tell you where the problem lies.

Also, did I post the Hex file for the TINKERERS_SB_NM?

Attached is a picture of a TX voltage pulse and a TX current pulse. This is what the wave forms should approximately look like.

Careful with the current measurement, not to damage the CRO. I use a 100mOhm resistor in series with the drain coil wire. A smaller resistor is even better.

Tinkerer

Now, that is funny, I can not add any attachments. I will send this off and try with a different browser.

[Tinkerer]

Ok cheers, I get it now. AC coupling, followed by injection of new DC level of a touch over 2v from battery ground. Which should allow the PIC's 5v span to safely cover the worst case scenario of 7v high, 3v low required by the 4066. Without the 56k resistor it wouldn't have gone low enough. 70k might be better though, just so its nicely centered, .5v over the requirements on both ends.

Have you given any thought to where you are going to put the PIC (ie. TX board or RX board), and how you are going to organize the power supplies if you start using its on-board ADC for audio? It would seem there would have to be some compromises.

Midas

Edit: No sorry all these different levels are confusing aren't they... The DC level you want to inject is 2.5v above -5v right? So I think what you want is another 100k to -5v..

The general idea is to keep all noisy parts together and away from the analog, where the noise is really not desired.

On the above circuit I have decoupled the audio transistor and added the capacitors to keep the hard switching square wave noise out of the supply.
In fact, I see no reason why the whole audio should not be on the TX board.

Tinkerer

[mickstv]

Hi Tinkerer, any chance you could post up a CRO shot of one TX pulse of the output, so that I can see what is expected to be seen. Maybe the CRO shot could be done via a second coil not in null ?

I roughed up a basic TX today and all I got was a over heated FET with lots of ringing. Maybe I did something wrong.




Cheers
Mick

[Tinkerer]

I probably should have mentioned that its also down to the duty cycle of the signal. I was just assuming that the signal lines spend the vast majority of their time low, which actually may not be entirely true for all sample schemes. You don't have a whole lot of margin for drifting around as you change the sample time\pulse length ratio so your probably best off putting a diode in as well.

Midas

Thanks for the excellent suggestion. The Sample pulses are between 5 and 10us high and the rest of the time low. The diode will save power.

Tinkerer

[Midas]

I probably should have mentioned that its also down to the duty cycle of the signal. I was just assuming that the signal lines spend the vast majority of their time low, which actually may not be entirely true for all sample schemes. You don't have a whole lot of margin for drifting around as you change the sample time\pulse length ratio so your probably best off putting a diode in as well.

Midas

[Midas]

OK, I see now. I could not remember any high pass filters on this design.

C32,C12, R61, R60, are level shifters.

The PIC and TX are running on the 0V-12V battery rail to keep the switching noise isolated as much as possible.
I also suggest to make 2 separate PCB's and a shield between to keep the EMI pf the TX & PIC out of the analog circuit.

The analog part is running on +/-5V centered on the 6V rail.

This makes the PIC pulse to be -6V as seen by the analog GND, so the C32 and C12 bring the pulse up and centered on the Analog GND.

I have updated the design and added a resistor of 56k to the -5V, so that the PIC pulse triggers the CD4066 properly.

Thanks for bringing this to my attention. I will post a revised version of the design in a few days, when all the mistakes have been discovered and corrected.

SO, PLEASE, EVERYBODY SEARCH MISTAKES AND MAKE SUGGESTIONS, SO THAT WE CAN POST ALL THE CORRECTIONS IN ONE SINGLE POSTING.


Tinkerer

Ok cheers, I get it now. AC coupling, followed by injection of new DC level of a touch over 2v from battery ground. Which should allow the PIC's 5v span to safely cover the worst case scenario of 7v high, 3v low required by the 4066. Without the 56k resistor it wouldn't have gone low enough. 70k might be better though, just so its nicely centered, .5v over the requirements on both ends.

Have you given any thought to where you are going to put the PIC (ie. TX board or RX board), and how you are going to organize the power supplies if you start using its on-board ADC for audio? It would seem there would have to be some compromises.

Midas

Edit: No sorry all these different levels are confusing aren't they... The DC level you want to inject is 2.5v above -5v right? So I think what you want is another 100k to -5v..