Oscilloscope bandwidth and multi turn presets, questions

[Denots]

Hi
I?ve been working on this on and off for the last couple of weeks and just discovered the forum, just in time too


I?m on step 3 now and at the point where an oscilloscope is needed to progress, spent the last week browsing different scopes but this is all new to me, I?ve picked a couple of potentials but I?m trying to figure out what bandwidth to get.
Can anyone tell me the best bandwidth for this circuit please


Also the R5, R37 & R14 multi turn presets have 3 legs and there are 4 holes, should I have soldered them in a straight line or was I right to put the middle leg to the outer hole


Many Thanks

edit: sorry about the question marks it doesn?t seem to like my punctuation

[homefire]

No Idea what your talking about. INSUFFICIENT information.

O Scope
Step Three
Eaaa?

[waltr]

Yes, Exactly Which detector kit are you building. Otherwise we can not answer your second question.
Probably the PCB was designed for two types of pots. Ones with the three leads in a straight line and the ones with leads in a triangle. LOOK at the PCB with a good magnifier and use your Ohmmeter to see if the two center pads are connected.

As for O'scope. I use a 30MHz 2 channel analog scope and works fine for testing/adjusting PI detectors.

[Machinist]

Maybe the fact that Denots has posted in the Minipulse Plus Forum is a clue to what he is building. Just saying

[Denots]

Sorry I should have been more clear, it’s the mpp Rev e, ok I’ll check that with my meter now
thanks

[Qiaozhi]

Sorry I should have been more clear, it’s the mpp Rev e, ok I’ll check that with my meter now
thanks

The PCB layout is designed to accept multi-turn trimmer pots with either 3 pins inline or with the middle pin offset. Both of the middle pin pads are electrically connected.

[Denots]

Thank you for your answers, I tested the terminals with my multimeter and like you guys said the two centre terminals are connected anyway so can go either way, on hindsight I should have tested that first but you live and learn.
As for an oscilloscope I have ordered a hantek DSO5102P which is 100MHz but can be upgraded to 200MHz with a simple software upgrade, should be plenty enough for what I need.
Thanks for your help, no doubt there will be more questions to come

[waltr]

Ok. We builds these detectors to learn.

That scope will be more than fine.
Hint: if you need to observe two signals use the external input for the trigger, say of the TX pulse control.
Now you have two channels to observe two other signals.

[green]

[QUOTE=waltr;259348]Ok. We builds these detectors to learn.

That scope will be more than fine.
Hint: if you need to observe two signals use the external input for the trigger, say of the TX pulse control.
Now you have two channels to observe two other signals.[/QUOTE

Good suggestion. I'm guessing Denots might be new to using a scope and PI detectors. Connecting trigger to pulse control is the key word. I learned the hard way the Tx pulse(fly back)can do some damage. Make sure probe is on X10 when connecting CH input to Tx pulse.

[Denots]

Ok. We builds these detectors to learn.

That scope will be more than fine.
Hint: if you need to observe two signals use the external input for the trigger, say of the TX pulse control.
Now you have two channels to observe two other signals.

Ok thank you for the advice, I’m not exactly sure what that means yet but I’m sure it’ll become clear when I’m using the new scope.
Thanks

[QUOTE=green;259350]

Ok. We builds these detectors to learn.

That scope will be more than fine.
Hint: if you need to observe two signals use the external input for the trigger, say of the TX pulse control.
Now you have two channels to observe two other signals.[/QUOTE

Good suggestion. I'm guessing Denots might be new to using a scope and PI detectors. Connecting trigger to pulse control is the key word. I learned the hard way the Tx pulse(fly back)can do some damage. Make sure probe is on X10 when connecting CH input to Tx pulse.

Thanks for pointing that out, your right I’m new to all this, I come from a raspberry pi background and have built many circuits using that but nothing as sophisticated as this, to be honest I’m not even that fussed about metal detecting, just seen the kits on the website and fancied the challenge.
Hat off to all you electronics gurus, some really clever stuff that just blows my mind

[homefire]

My Lenovo computers BUILT IN BATTERY took a dive. Ordered new and took four days to arrive and get installed. Not bad I'm thinking. How ever it would seem I did in fact miss this boat.

Good stuff you all jumping on this one.

[Denots]

Oscilloscope turned up today and managed to get everything dialled in and working as described in the instructions.
Onto step 4 now
thanks for all your help

[Machinist]

Glad you have it sorted now Denots.

I have just got this kit myself but have not started it yet. I have a different simpler project to have a go at first as it is a long time since I have built any electronic circuits and need to get my soldering skills honed again.

I am coming at it from the opposite side to you, I am a metal detectorist and fancy having a go at building a detector for myself. I have been using pulse induction machines for nearly 30 years now and I have had one of George Overton's original Crossbow Classics (No 10) from new.

Good luck with the build.

Ray

[WM6]

I have ordered a hantek DSO5102P which is 100MHz but can be upgraded to 200MHz with a simple software upgrade, should be plenty enough for what I need.

No doubt.

In general, if we stay with o-scope measurement in metal detector field, almost all available scopes suit
to our needs regarding frequency bandwidth (even 15MHz is full enough in metal detectors field).

With detectors (not only PI) we are facing with tiny signals, so it could be more important to take care about
detector vertical sensitivity than its frequency bandwidth.

This way, it is better to chose scope with 100MHz bandwidth and 1mV/div vertical sensitivity, than scope with
200MHz bandwidth and 2mV/div vertical sensitivity.

Currently probably best bang for buck is Siglent SDS1202X-E with 200MHz bandwidth and 0.5mV/div (!) of
vertical sensitivity. Available for about €400 here in EU (VAT inclusive).

[Denots]

Glad you have it sorted now Denots.

I have just got this kit myself but have not started it yet. I have a different simpler project to have a go at first as it is a long time since I have built any electronic circuits and need to get my soldering skills honed again.

I am coming at it from the opposite side to you, I am a metal detectorist and fancy having a go at building a detector for myself. I have been using pulse induction machines for nearly 30 years now and I have had one of George Overton's original Crossbow Classics (No 10) from new.

Good luck with the build.

Ray

I think you’ve made the right choice there, it’s not as easy as I thought it would be, just identifying some of the components has been a challenge on its own, thinking I should have started on an easier one first but that was all that was in stock at the time.
A friend of mine is well into detecting and I do go out for a wander with him from time to time, he kept on at me “you should get a detector” my reply is “rather than buy a detector I’d rather build my own then when it’s finished fit it to a remote control car and have it drive around a field marking everything it finds using gps while I sit at the side and watch”
so here I am lol

No doubt.

In general, if we stay with o-scope measurement in metal detector field, almost all available scopes suit
to our needs regarding frequency bandwidth (even 15MHz is full enough in metal detectors field).

With detectors (not only PI) we are facing with tiny signals, so it could be more important to take care about
detector vertical sensitivity than its frequency bandwidth.

This way, it is better to chose scope with 100MHz bandwidth and 1mV/div vertical sensitivity, than scope with
200MHz bandwidth and 2mV/div vertical sensitivity.

Currently probably best bang for buck is Siglent SDS1202X-E with 200MHz bandwidth and 0.5mV/div (!) of
vertical sensitivity. Available for about €400 here in EU (VAT inclusive).

Thank you for clearing that up. When watching videos about scopes I learned that bandwidth is important and depending on the bandwidth of the scope depends on the results you get, I guess I got sort of transfixed on that when really it didn’t matter for this circuit. Tbh I don’t understand it all, this is a huge step forward from what I’m used to, I build circuits by trial and error normally, with this project I find myself doing things that I haven’t got the foggiest idea about, like trying to work out the inductance of a coil, spent a whole week playing around with that and still haven’t got a clue lol.