Replies to Minipulse Plus

[Davor]

That was fast

[6666]

The beast lives, nice pulse at TP1.

[6666]

So far both +5 & -5 volts works ok, I must admit I am not too keen on the tiny solder pads.

If you have the kit no plugs or pins are provided for PL 1-5, you need a trip to your parts store
here is a tip, if you want plugs with wires have a look in your R/C model shop for servo leads.

[6666]

Kit has arrived, Thanks Andy.

[Qiaozhi]

more REVB boards have arrived
I have updated the shop stock levels for pcbs and kits
As this was a bigger batch of pcbs and the GBP is strong against the USD at the moment they have worked out cheaper

Please note that the new set of boards are actually REV-C.

This revision has fixes for the two small errors mentioned in the Build Document (Step 2 and Step 9), and an additional testpoint where you attach a ground probe. However, the recently discovered sync issue is not fixed, and requires you to not fit R5, R9 and Q2. These components will not be included in the Silverdog kits.

I will update the Build Document shortly and add a new REV-C thread with the latest details.

[silverdog]

more REVB boards have arrived
I have updated the shop stock levels for pcbs and kits
As this was a bigger batch of pcbs and the GBP is strong against the USD at the moment they have worked out cheaper

[Davor]

Chip replacement with a more contemporary ones is often working good, provided a new chip is in fact better for the job. For this function we need a FET input op amp with noise performance better than 100nV/sqrt(Hz) at 1 Hz, and over 20V/us slew rate. As low the 1Hz noise, and as high slew rate, the better. TLE2072 is in that sense somewhat better than TL072, and less so against LF353, as LF353 has less noise.
I found a distributor that will send me a TLE2072 (eventually) that I'll compare with other chips, but for the time being, LF353 will stay.

I'll concentrate my efforts to building the device and a coil, and to designing a GB board ... unless someone beats me to it. I've let all the details necessary for making it.

[sinclairuser]

As mentioned before, I'm considering replacing TL062 with LF353, and adding some 100k in series with the FETs gates. I made a simulation in LTspice that clearly points to the sources of charge injection. The attached project contains lots of different opamps and many more FETs. I also checked TLE2072 model, and it shows considerable improvement, but I can't buy it here. Besides, LF353 has superb 1/f noise.

thanks for the file davor, its a shame about the tle2072, i will try it my end if it works out i could allways post you a couple of samples.
if we try different approaches, we will know what works and what doesn't.
i for got to say before to everyone dont use a tle2072, unless you have a tle2071 to replace the tl061, when your going for lower noise choices like here, replacing one chip is a waste since noise could come from the 061, i have found these newer versions benefit from this approach.

[Davor]

As mentioned before, I'm considering replacing TL062 with LF353, and adding some 100k in series with the FETs gates. I made a simulation in LTspice that clearly points to the sources of charge injection. The attached project contains lots of different opamps and many more FETs. I also checked TLE2072 model, and it shows considerable improvement, but I can't buy it here. Besides, LF353 has superb 1/f noise.

[Qiaozhi]

Hi George,
R5, R6 or Q2 suggest this should read R5, R9 or Q2 since removing R6 will remove the 100k preset...!
Also I have just completed building the MPP and the build went very smoothly the only part missing from the Components List is R2 (10R)..!
I plan to run some tests before posting my results within the next few days but so far it appears to be working ok about 30cm to a coin..!

You are correct. That was a typo, and should have said R9. In fact, I did update the Minipulse Plus REV-B thread at the same time, and put the correct information there. Unfortunately I posted the wrong info in this thread.

The missing R2 error has been added to the Minipulse Plus REV-B thread. The document will eventually be updated when we move to a REV-C layout.

You seem to getting excellent results with the MPP, and hopefully this will encourage others to follow suit. If you want to send me some photos by email, plus details of your coil, and any test results, etc., I will create a new [locked] thread to display everyone's efforts. The reason for locking the thread is simply to keep it clear of the inevitable "Well done" and "Jolly good effort" sort of posts. As you appear to be the first to create a successful build, you will be top of the list.

[Davor]

The Silverdog kit should match the MPP Build Document, and none of the suggested changes by Davor and others are included in the current revision (REV-B). If you construct a kit from Silverdog, then it is guaranteed to work. However, it is possible that some substitutions may occur due to availability, such as replacing the TL062 with a TL072. This will not affect the basic operation of the detector.

I'm not considering any mods that would affect the board function, apart from the GB module, and it all is just considering replacements of the project parts with clear upgrades. I'd suggest you to use quality sockets for all ICs, and also use sockets for FETs if you plan to experiment with those.
I'm about to design an add-on board for GB, and its wires will be placed in the respective pin holes on the vacated MC14538 socket(s). So even with GB you can use the existing board as-is.

[Dean Sarelius]

I've been looking at the sync problem this evening, and ...

The conclusion of my investigations is that there is no requirement to fit either R5, R6 or Q2.
I will remove these in a future update.

Hi George,
R5, R6 or Q2 suggest this should read R5, R9 or Q2 since removing R6 will remove the 100k preset...!
Also I have just completed building the MPP and the build went very smoothly the only part missing from the Components List is R2 (10R)..!
I plan to run some tests before posting my results within the next few days but so far it appears to be working ok about 30cm to a coin..!

[sinclairuser]

I am a little lost in all this changes, corrections and improvement ideas.

Can someone tell me (with purchased silverdog's Minipulse kit in mind), what are now necessary changes and corrections, regarding Minipulse kit, if any? Will kit works as is or not?

the posted project in the build document, and the kit are tested and working 100%.
we are just looking for anything we can do on later revisions, and looking for mods, simpler or better ways of doing the project thats all.

[Qiaozhi]

I am a little lost in all this changes, corrections and improvement ideas.

Can someone tell me (with purchased silverdog's Minipulse kit in mind), what are now necessary changes and corrections, regarding Minipulse kit, if any? Will kit works as is or not?

The Silverdog kit should match the MPP Build Document, and none of the suggested changes by Davor and others are included in the current revision (REV-B). If you construct a kit from Silverdog, then it is guaranteed to work. However, it is possible that some substitutions may occur due to availability, such as replacing the TL062 with a TL072. This will not affect the basic operation of the detector.

[WM6]

I am a little lost in all this changes, corrections and improvement ideas.

Can someone tell me (with purchased silverdog's Minipulse kit in mind), what are now necessary changes and corrections, regarding Minipulse kit, if any? Will kit works as is or not?