My Surf PI works - thanks Silverdog and ApBerg

[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

[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.

[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?

[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]

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.

[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

[Rov]

Hi Ant,think you from Oz? am I correct.Im also here,so if you have an issue with your build/construction,give us a quick pm.an I may be able to help you.
regards rov

[ant]

Hi Ap

Thanks for your help so far. I didn't get a chance to have another look yesterday. I do think there is something wrong, the TUNE dosen't work as you describe. The pots are mounted off the board with wires, but I also tried mounting the pot on the board with the same results. I think i'll have to check each component against the schematic

It does generally work, it can detect my metal ruler at about 20cm, a gold (white gold is all I have) ring at about 5-10cm. Considering I'll only be using it for diving (not scuba) maybe that will be good enough cause I don't want to dig too deep underwater anyway

Anyhoo, I'll have another look at it tonight.

Thanks,
Ant

[ant]

Hi again Ap

Just saw your post at http://www.geotech1.com/forums/showp...2&postcount=29, Thanks, should help when I get home I'll check my board.

[ant]

mmmmm

So i got home from work and decided to switch boards for the second one I got. Working much better, no problem with the tune dial. I think I just need to work on a better coil and hopefully get more depth, only getting about 5-10cm for a (au) $1 coin.

So back to the old board, I've checked all the cap and resistor values against the bom, and Aps diagram, next I'l try swapping the IC's, but that can wait for another time.

Anyway tea's ready, thanks for everyons help

[ApBerg]

So i got home from work and decided to switch boards for the second one I got. Working much better, no problem with the tune dial. I think I just need to work on a better coil and hopefully get more depth, only getting about 5-10cm for a (au) $1 coin.

So back to the old board, I've checked all the cap and resistor values against the bom, and Aps diagram, next I'l try swapping the IC's, but that can wait for another time.

Anyway tea's ready, thanks for everyons help

Hello Ant,

You must detect wedding rings and medium size coins in the 20 cm+ range...good to tray a different coil.... you have some info on the coil you use now ?

At the and it will work ok !!

Regards.

Ap

[ApBerg]

Hallo Ant,

To be shure that things indeed work ok I have made some checkings.
If you leave out the tune pot (and think the offset pot) the surf detects a ring as on the photo at some 15 cm. With the tune pot in place and at max ( just getting threshold ) it is 25 cm + 'Look at the coil, normal isolated wire some 20 turns (I think) works good.
The most importend adjustment is the delaypot.... look next message...

[ApBerg]

..... with the delay pot you set the sample window's: the 4093 pin 3 and 4 close the switches from the 4066 in time shift , the LM 358 can now see the 'receive signal' coming from the NE5534 at 2 different time's .. this lets the detector know if there is "anything" in the receive signal. So the delay pot is imported the fist window to close to the transmitpuls give's some problems.... to far less sens.
Wel look at the scope samples ... hope this helps ..

Best regards.

Ap

[ant]

Hi App

Thanks for your ongoing help. I hooked up the scope and started to understand the circuit better, and my delay/tr looks the same, the delay pot does the same as yours.



I disconnected the TUNE and OFFSET and managed to detect the gold ring at about 80mm. So I made two more coils;

PVC; 214uH - 1.6Ohm
Brown hookup; 267uH - 2.5Ohm
enamel; 282uH - 1.6Ohm

But much the same results, I'll study coil making tomorrow and try again.

Here are some pictures of the case anyway, not ready for water testing yet but not far off.

Thanks,
Ant

[ApBerg]

Hi App

Thanks for your ongoing help. I hooked up the scope and started to understand the circuit better, and my delay/tr looks the same, the delay pot does the same as yours.



I disconnected the TUNE and OFFSET and managed to detect the gold ring at about 80mm. So I made two more coils;

PVC; 214uH - 1.6Ohm
Brown hookup; 267uH - 2.5Ohm
enamel; 282uH - 1.6Ohm

But much the same results, I'll study coil making tomorrow and try again.

Here are some pictures of the case anyway, not ready for water testing yet but not far off.

Thanks,
Ant

Hello Ant,

You have done a lot work... nice control panel ! Do you have special potentiometers for it that are waterproof ?
Your detectors sens. is to low , if al is ok it must detect over 25 cm, I am shure you wil get that.

Regards.

Ap