Replies to Minipulse Plus

[6666]

From the little bit of testing I have done with a 280uH coil, and looking at tp3, this REV-B preamp looks fast.

[joop]

Ah, excuse my misunderstanding. Okay about the coil George, will report back!

[Qiaozhi]

My coil is 330 microHenry with a fairly large diameter: 32 cm. Using the damping resistor that came with the kit. I have been looking at pics of the original mini-pulse, the coil seems a lot smaller. Maybe around 20 cm diameter? I will try a different coil and report back on this.

https://www.ahrps.org/forums/file.ph...name=photo.JPG

What johnandles means is that we cannot view the image in your link. It gives the message "Permission denied: links to files in the forum are only allowed from the forum itself."

The original Minipulse coil is 8" diameter. Also, try moving the coil into different orientations and watch if the noise level changes. It may all be external noise.

[joop]

Permission denied...

Me thinks everything on the internet is in the public domain...

[johnandles]

I will try a different coil and report back on this.

https://www.ahrps.org/forums/file.ph...name=photo.JPG

Permission denied...

[joop]

What are the details of your coil? The timebase on your scope is set to 50us, and the RX signal is still settling. Or perhaps your damping resistor is not the optimum value?

Here is a scope shot of my MPP. Channel 1 is connected to TP1, and channel 2 is connected to TP3. As you can see there is some noise on the signal, but nowhere near as much as your's, and this is running from a bench power supply (which is also noisier than using batteries) and next to two computers, and low-wattage fluorescent lighting. I'm using the original Minipulse (500uH) coil, and you can see that it settles within 25us,

My coil is 330 microHenry with a fairly large diameter: 32 cm. Using the damping resistor that came with the kit. I have been looking at pics of the original mini-pulse, the coil seems a lot smaller. Maybe around 20 cm diameter? I will try a different coil and report back on this.

https://www.ahrps.org/forums/file.php?2,file=78,filename=photo.JPG

[6666]

Despite the fact that I've built 2 Minipulse Plus detectors using the Build Document, and Andy (Silverdog) and Dean Sarelius have both completed successful builds, no-one has spotted that one so far.

TP10 doesn't exist in REV-B. That should of course be TP9.
In REV-C, TP10 is the ground probe connection.

I've added a note in the Minipulse thread(s), but will not update either document at this time. Eventually, by REV-D(?) we might get rid of all the errors.

All good, cheers.

[mickstv]

I was wondering about limiting Tx current. There is a fairly simple way of doing it, and there was a solution by our PiTec that uses continuous adjustment still found here: www.tb-electronic.de/pi_tech/pulse_cc_circuit.pdf
I'm expecting some improvement in a sense of separating the leading edge against flyback, and also some noise improvement, but I also wish to hear more about it from first hand experiences, if any.

Hi Davor, a simple solution would be to add the circuit I posted link below, only a few components needed.

http://www.geotech1.com/forums/showthread.php?21501-PI-current-pulse

[Davor]

I was wondering about limiting Tx current. There is a fairly simple way of doing it, and there was a solution by our PiTec that uses continuous adjustment still found here: https://www.tb-electronic.de/pi_tech...cc_circuit.pdf
I'm expecting some improvement in a sense of separating the leading edge against flyback, and also some noise improvement, but I also wish to hear more about it from first hand experiences, if any.

[Qiaozhi]

I am attempting a REV B build, just finished the RX stage. The signal at TP3 seems a bit noisy, is this normal? This is without the sampling integrator added, which starts with R18. Picture attached. Top trace is the flyback signal.

[ATTACH]30670[/ATTACH]

What are the details of your coil? The timebase on your scope is set to 50us, and the RX signal is still settling. Or perhaps your damping resistor is not the optimum value?

Here is a scope shot of my MPP. Channel 1 is connected to TP1, and channel 2 is connected to TP3. As you can see there is some noise on the signal, but nowhere near as much as your's, and this is running from a bench power supply (which is also noisier than using batteries) and next to two computers, and low-wattage fluorescent lighting. I'm using the original Minipulse (500uH) coil, and you can see that it settles within 25us,

[joop]

I am attempting a REV B build, just finished the RX stage. The signal at TP3 seems a bit noisy, is this normal? This is without the sampling integrator added, which starts with R18. Picture attached. Top trace is the flyback signal.

[Qiaozhi]

I tried simulating a PSU with only MOSFETs, and it is a no go. Duty cycle is too asymmetric for any meaningful currents so LT1054 that is.

Thanks Davor. I'm not surprised by your results, but it's very good that you've tried to find a working solution.

I don't know how many MPP boards have been shipped by Silverdog, but I'm surprised that more members are not displaying photos of their working creations. So, to anyone who has built an MPP, please email the photos to me (with any [useful] comments) and I'll add them to the "Completed Minipulse Projects by Geotech Members" thread. At the moment the Aussies are in the lead.

[Davor]

I tried simulating a PSU with only MOSFETs, and it is a no go. Duty cycle is too asymmetric for any meaningful currents so LT1054 that is.

[Qiaozhi]

Step 9 both build docs says


Where is TP10 ?

Despite the fact that I've built 2 Minipulse Plus detectors using the Build Document, and Andy (Silverdog) and Dean Sarelius have both completed successful builds, no-one has spotted that one so far.

TP10 doesn't exist in REV-B. That should of course be TP9.
In REV-C, TP10 is the ground probe connection.

I've added a note in the Minipulse thread(s), but will not update either document at this time. Eventually, by REV-D(?) we might get rid of all the errors.

[6666]

Step 9 both build docs says

Adjusting the Audio [threshold] pot will produce a DC level from -5V to +5V at TP10

Where is TP10 ?