My Surf PI works - thanks Silverdog and ApBerg

[ApBerg]

Hello Ant,

If you use the tune potentiometer placed as on the PCB it can be that it works counterclockwise,
The tune has to work as normal for a detector, at turning up the sound gets louder little by little... ( but possible you have to turn the potentiometer "low" if it is placed as on the board, test this out) If no succes can you make a close up photo ?
At wat distance you can detect a gold wedding ring?

Best regards.

Ap

[ant]

Hi ApBerg

I'm not sure my tune dial is working correctly, when I turn it up, I just get a beep each aprox 2 seconds, should the tune do this? Or should it just be a background noise like the threshold on my Minelab?

Thanks,
Ant.

[ant]

update: Forget that last post, I was confusing myself, and not reading the component names on the PCB proberly(it is a bit confusing on the pcb).

Now I've changed R18 and R22 around to the correct values and its much better, still testing

[ant]

Getting closer

Hi everyone

I've been focusing on the housing lately, but just trying to put it all together at the moment.

I'm a bit confused with the TUNE dial, I change it but I don't get a sound from the speaker. Looking at the circuit diagram compared to the board layout, they don't seem to match, In the circuit diagram, R18 (47k) goes between V- and pin 3 of the tune pot, but on the board R18 isn't connected to the pot; I think R18 and R22 have been changed around. Can someone else with a working tune dial (actually get a threshold) tell me the values of R18 and R22?

[SVEN1]

Just about got all my parts together to build up three boards. Took awhile to scrape up all the parts at good pricing. Just waiting on the balance of parts, then need to acquire some wire for a coil and my winter projects will be good to go.

[ApBerg]

Hi Congratulations on this Fine design,Hope it works well for all builders of this revised design.
ApBerg,Are there other Notes an Errata that builders should be aware of for a successful build?
eg.other wire links,as there appears other unused pads on the pcb.or a substitution of parts.eg.2n3906 can use BC327 or changing 1n4004 diode to Fast recover Diode etc.
I notice on some pictures here on the forums from recent past ,extra Capacitor at position C16 on pcb.being a .1 MKT style and extra GreenCap Poly with unknown value beside it.??
I havent built this unit yet myself,waiting on parts?So would wish that my parts list as other builder,is true an complete?
Thank You,
Rov

Hello Rov and others,

Thanks for your positive interest. I think that there are not much problems in building the board. Some background in electronics is off course welcome… !
There are some different types transistors possible , but the used parts are very common so I think it is not hard to find them. If you use other parts take care for their pin configs!
For the coil you can find very much info on Geotech , the coil is not very critical and many options work !
The adjustments for the potentiometer can made by trial and error, no great risk in destroying parts. The adjustments for the volume and threshold potentiometers are very clear I think, the delay is somewhat stance… it has much influence on the sensitivity from the detector, searchs for the point where you have a good sensitivity for a golden ring, if adjustment is to far towards the transmit pulse, the detector will not work anymore, no harm is done, just turn back to the point where you had good sensitivity.
The adjustment from the offset potentiometer is the ‘most invisible’ …set the potentiometer in mid position at the first startup. If you have a scope than adjust the dc offset as normal. If you have not a scope look at the mail above I send to Ant. I think it is possible by listening to the sound if the adjustment from the offset potentiometer is at a good point. If anyone has works this out … please give your opinion ….

Of course it is very nice from Silverdog that he gives so a good service in offering very good quality boards for a very.. very.. low price’s! ( Think he cannot make a profit..) This makes it possible for large group friends to make this detector. It is not to hard now to make a good small Pi detector that works very good. But there is always a risk that there is a bad part ..or a mistake from the builder that makes it hard to get things going…

If there are problems …. ask on this forum..

Best regards.

Ap

[Rov]

Hi Congratulations on this Fine design,Hope it works well for all builders of this revised design.
ApBerg,Are there other Notes an Errata that builders should be aware of for a successful build?
eg.other wire links,as there appears other unused pads on the pcb.or a substitution of parts.eg.2n3906 can use BC327 or changing 1n4004 diode to Fast recover Diode etc.
I notice on some pictures here on the forums from recent past ,extra Capacitor at position C16 on pcb.being a .1 MKT style and extra GreenCap Poly with unknown value beside it.??
I havent built this unit yet myself,waiting on parts?So would wish that my parts list as other builder,is true an complete?
Thank You,
Rov

[ApBerg]

Hello Ant,

Have you made the small jumper (link wire) connecting the 4066 to MPSA13 ?
you find this link on top R16

Succes

Ap

[ant]

Rov; Thanks for the tips, I briefly hooked the scope up to TP1 and TP2, changed the pots and saw the scope change, but I think I need to understand the circuit before I can understand what I see on the scope. I'll do a bit more study over the weekend.

Micheal; That would be great if Carl approves, can you PM me a pic in the meantime, I'm thinking I should try another coil for experimenting.

Plumabob; Thanks, hope all goes well with yours.

Apberg; Thanks for the tips, good to know where I need to start. I tried to change the threshold/tune potentiometer but can't get it to give a constant buzz, I really need to study the circuit.

Thanks everyone

[Micheal]

I have an original SURF Pi coil that I have opened up for experimental purposes ....im not sure if I am allowed to post pictures of it as it is an original whites coil ....If carl okays it I can post them here ...
just trying to help all the Surf pi builders

[Rov]

think if you look at your pcb you will see some pads there with TP or test points these are for your scope or meter to check from.at relevant stages of the circuit.
connect your scope probe to these,an ground connection also.
What the wave forms an signal properties an values are Im not sure.
The creator of this PCB design can supply you with these an what you should be seeing.
I havent built this unit yet so I cant tell you difinitively myself.

[ant]

I do have a scope

Hi ApBerg

I do actually have a scope, and was going to go thru the circuit diagram to see what I should be looking at with it. Just so you know, I am a novice with electronics but I do want to understand how it works. Just to get me started, where would I hook the scope up?

Thanks, Ant

[plumabob]

Waiting for mine to arrive. Great job! Hope mine works out as well!

Bob

[ApBerg]

Hi GoldFinder

This is my first built MD, so I'm trying to get my head around the circuit and how it actually works. At the moment it's not great, but that might be because I'm testing it in a steel shed, with reinforced concrete floor, a steel workbench and pretty much a bunch of steel around me. So yes I will test the distances, but it might be a week or two before I can get it out of the shed in a working form. BTW, I'll have to use Australian coins, but should get an idea.

Thanks everyone.

PS. Just on the point of trying to understand how it works, is it recommended to build one of the Hammerhead varieties? (I think I just answered my own question)

Hello Ant,

Start with all the potentiometers in mid position, then tune the threshold/tune potentiometer at the point that you get some sound, tray if you can get some detection for a solid gold ring. If so adjust the delay potentiometer to the point that this ring is detected at the best distance . If you turn to far there is suddenly no detection anymore, no harm is done just turn back again to the best point you had.
The offset potentiometer is a problem if you have not a scope. But... if you have a good detection for a gold ring then swing the ring fast from left to right and right to left over the coil and listen to the sound, adjust the offset potentiometer so that the sound response in both directions is the same, tray this with different speeds. Let us know if you can use this setup ?
If somebody has a better way...

A solid gold ring must be detected at some 23- 25 cm (some more if a good coil is used)

Succes

Ap

[WM6]

PS. Just on the point of trying to understand how it works, is it recommended to build one of the Hammerhead varieties? (I think I just answered my own question)

HH is best PI learning platform because of many controls it offer, bur Surf PI as first step cannot be wrong decision.