Rev D Build #2 Started

[geoscash1]

Thank you Chet,

Excellent, got home from work and tried it at 0.2ms/time div and it ends up approx. 4.5 divisions between the pulses so a resistor change may be in order to up the freq pps to get closer to the 1000hz/1000pps.

Other than that it looks like its close to spec so may move on to step 5, I'll jump over to KRinAZ's thread and see what if any changes/mods were made to this portion
of the circuit to get it closer to build doc spec.

Thank you and a sincere appreciation for the help and advice.
Geo

[geoscash1]

Step 5 - RX pre-amp

Step 5 RX pre-amp components installed, tested tp3 using scope channel 1 set to 1v/div at 50us/time div. Soda can makes a nice smooth low voltage change to wave form.





Good to go on to step 6....

[6666]

Be carefull when you get to step 6 the wording is talking about the width of the pulse, which gives the delay.

[geoscash1]

Step 6 Sample pulse generator

Be carefull when you get to step 6 the wording is talking about the width of the pulse, which gives the delay.

Hey thank you 6666 for the heads up, much appreciated... I have been reading thru the manual on my scope and playing with different settings just to get a better feel for what it is showing me, I'll get there.. Its hard to teach old dogs new tricks but with a little patience and practice, it can and will happen...

Step 6, Sample pulse generator components installed, tested TP1 w/channel 1 @ 1v/div/20us time and TP5 w/channel 2 @ 1v/div/20us time, PL3 jumpered from pin 2 to 1, triggered off channel 1. Adjusted R6 to give 22us width on channel 2 width. Everything seemed to go fairly smooth to this point and looks good on the scope, everything is working so far...






Done for tonight, will take it up a bit more tomorrow after work. Hope everyone has a great day,
Geo

[Chet]

Step 5 RX pre-amp components installed, tested tp3 using scope channel 1 set to 1v/div at 50us/time div. Soda can makes a nice smooth low voltage change to wave form.

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Good to go on to step 6....

Hi Geo

You have some high frequency noise that shows up after the receiver signal is sloping up. It is probably from florescent lights, computer or some other electronic device. Try turning things off and move your coil away from your work area. I set mine on a plastic waste can on the floor to elevate it above any nails and away from metal table legs.

Have a good day,
Chet

[geoscash1]

Followup to high frequency noise

Hi Chet,

Yep, you are correct, I have a twin tube florescent above my work space and that definitely creates havoc at times when trying to do stuff. I turned it off and took another pic and shows it clears up and cleans up the trace/wave. And thank you for the scope shots, very helpful.


Tested the following from step 6:

Main sample delay = 22us (scope settings 2v/div 20us/time delay - TP5)

Secondary sample delay (EFE) = 100us (actual 102) + main sample delay 22us (scope settings 2v/div 20us/time delay - TP6)

Main sample pulse width = 58us (scope settings 2v/div 20us/time delay - TP7) Approx 57us

Secondary sample pulse width = 58us (scope settings 2v/div 50us/time delay - TPeight)


Moving on to step 7.. Have a super night, see ya tomorrow evening.
Geo

[Qiaozhi]

Moving on to step 7.. Have a super night, see ya tomorrow evening.

Well done Geo. This is the correct way to build this project - step-by-step.
It's so much easier when you RTFM.

[geoscash1]

Well done Geo. This is the correct way to build this project - step-by-step.
It's so much easier when you RTFM.

Thanks Qiaozhi, I agree whole heartedly and it is basically how I do most any of these projects if there is a manual to follow. Ironically, this is exactly how I did build #1 but now I believe I know what I did, I shorted the 8 pin chip holder to the board at U9 between the board and holder with solder bleed so this time I am being more meticulous in my soldering. That first board should have went just as well but my hurried soldering mistakes cost me on it..

[geoscash1]

Step 7 Sampling Integrator

Step 7 Sampling Integrator components installed, tested TP4 with scope, pin 2 of PL3 jumpered to pin 1 and confirmed a nice DC voltage increase when target was swung/placed over coil. Scope settings used, channel 1, 5vd/20us/time delay (time delay not needed for test). The voltage change measured with my multi meter was from 0.8v to 4.0v (I misplaced my meter alligator clip so couldn't take a pic of meter at the same time but will tonight when I find it).

Step 7 components installed



Good to go and move on to step 8, have a super day..
Geo

[geoscash1]

Step 8 Second Integrator

Step 8 Second Integrator, components installed.

Test TP9 with PL3 still jumpered from pin 2 to pin 1 and with scope set to channel 1 @ 5v/div. Adjusted trace so it was centered on scope, turning the threshold/audio pot increased the DC voltage on screen to +5. Adjusted scope accordingly to center again, retuned the threshold pot to 0 then turned the board back on to see the DC voltage swing from -5 to +5.

Tested with soda can and can see good voltage increase. Then held soda can over coil for a few seconds and the +DCv settled back to the zero line on scope so the SAT is working perfect.

Perfect and just as explained in the build doc.

I tried to adjust it so the voltage level was approx. -1.5v but had difficult low stuttered tone. Lots of EMI in garage and such so getting a slow steady "growl" was difficult but definitely can be adjusted properly once out and away from the local EMI. Set to approx. 1.2/1.5v for time being.

Second Integrator parts installed

TP9 Dc voltage swing - 0v

TP9 Dc voltage swing - +5v


Everything tested perfectly according to build doc so far and is going nice and smoothly so moving on to step 9.
Geo

[geoscash1]

Step 9 Audio/VCO

Step 9 Audio/VCO components installed, finished testing on TP9 with scope, settings channel 1 @ 5v/div. Adjusted audio as best I can inside my EMI infested garage so now the Minipulse plus is finished. Definitive -5v to +5v using front panel threshold/volume pot and have a final setting of approx. -1.3v based on scope.

Coil tests - Detection with 7" inch round 24awg magnet wire bundle wound coil is:

US Quarter - 7"
US Nickel - 9"
14k gold wedding ring - 7"

The piezo is not a friendly sound so I will change to an 8 or 32ohm mylar cone speaker. The piezo has to much of a high pitch squeal and doesn't make for the best
trying to set audio correctly.

BOOM... She is done and working well, Now we can move on and try some of KRinAZ's mods to see how I can improve it, different coil (spider/basket), litz wire, ptfe and some resistor changes.



Thanks for a great little project, much happier this time around...
Geo

[WM6]

The piezo is not a friendly sound so I will change to an 8 or 32ohm mylar cone speaker. The piezo has to much of a high pitch squeal and doesn't make for the best trying to set audio correctly.

Take piezzo transducer with bigger diameter (2" dia par example).

[Chet]

Hi Geo

Good work! The small speakers vary a lot in volume and quality. Generally the the larger diameters are better.

Have a good day,
Chet

[godigit1]

Hi Geo,
Nice thread I wish I would have had this on my mini pulse build!
Glad this one went perfect for you. I am at the mod stage my self so I look forward to your future posts!
Best
Digit

[geoscash1]

Changed the speaker

Hey guys, thanks for all the help with the scope info and screen shots, it was very helpful and very much appreciated.

As for the minipulse, I changed out the little 1/2" round piezo for a 1-1/4" 8 ohm mylar cone speaker and wow, what a difference just that made in the audio.

Will be trying a few of KRinAZ's mods this weekend to see what it will do. I had a spider/basket wound coil on a form that has 21awg mag wire and is 305uH and gave
it a try and it is a noticeable difference too compared to the bundle wound 24awg magnet wire coil I used for building with. So I will be building a new one with litz 250/44 to see if that makes any difference as well.


Anyway, you all have a great day and I'll keep this thread updated with results.
Geo