Goldscan IV : my proto works

[Max]

Hi all,
I've just finished working on sheet 3/3 part of the schematic , mounting all the stuff on a protoboard and then connecting to my power supply.
It works !

Or maybe seems, well I have a response using 1 euro coin at about 27 cm (at the moment):

At max sens (now using 15 us delay)
- 27 cm --> start to click (all metal mode)
- about 20 --> vco goes in hundred hz freq
- about 15 cm --> screams (loud and steady tone)

coil used is (matching approx the schematic value)
- 8'' (20cm) od
- 28 turns of 0.375 enamelled copper wire (transformer like)
- shield is conductive (aluminium) mylar film 35micron
- cable is standard rg-58au
- R= about 2.9 ohm L= (measured) 412uH

-IRF740 little warm
-circuit stabilize after about 5 minutes
-used also jfets J112 instead of J113 --> not relevant differences
-used NE5534AP instead of uA709 (metallic case) : relevant differencies

It's all for now.

Best regards,
Max

[kt315]

biggest greetings Max! can you speedy look attachment on a subject of mistakies? tia!

[johnno]

gs4

biggest greetings Max! can you speedy look attachment on a subject of mistakies? tia!

Hello good post!
is the pcb on page 5 good,no errors?
has someone built this?
I see it is a thru hole board with SMT resistors on the back.am I correct?
All help welcomed thankyou
johnno

[Max]

Hi KT315,
I'm still working on the protoboard version and also in making a thru hole PCB.
Thanks for the useful file. I'm watching for mistakes. Untill now I found only the differences in the reset stage :

- two sources of J113s to ground
- the 470K resistors (motion and autoretune mod) just don't know why R50 should be 10K (seems to me R50 and R49 must be equal - 470K works well on my proto but I prefer motion type detector so I've used a switch to disconnect them both).

and preamp substition (but now it's not the original gs4 here):
- i make the same thing ne5534ap is a really good preamp here

The PCB in the file seems smaller respect to the one I'm designing at now ( this guy -Alex- seems have done a really good reverse on GS-4 and new PCB design).

I had problems with the supply stage (555 voltage doubler) becouse of the noise propagation on the pream section (I'm using NE5534 after a try on different uA709-metallic case revealed they are not really stable --> lot of drift). Think one can use 7660 instead of the old fashioned 70's 555/bjt design.

Also, as indicated by yellow squares, capacitors must be mached in values, becouse of the simmetry of the circuit (I've measured a lot of them before found same values in less than 1% of nominal value). Then also I've used schottky diodes (BAT73) in the supply section and tried them on the timing stage: in supply they improve efficiency but there are no difference in timing stage commutation, now I have 1N4148 on timing that are OK.
Also I've tested TL084 instead of TL064 : are the same in noise level , but more consumption. I think one can use a better LS404 (STmicro) or MC33079(motorola) to have the best here.

I think also the 14.4 batt pack was not a good choice; here one could use maybe an LM2990T-12 (LDO -12 regulator) to use directly a lead acid type battery (say 12V nominal - 1.2 A/h or more) to improve battery life or to maximize peak current on the coil. But I never tested if it works really. Another choice could be a NIMh battery pack (say 15V - 2700ma/h) : I'll try it soon.

In off mode one have the best results in air tests. When switching to GND-balance (all metal mode) performance loss is about 10-15 % in air.
Sel 1 and Sel 2 seems to be operated only if needed and by an expert user to "say" if there is iron or other stuff: just GS4 is not really discriminating , so a big junk of iron, and actually also a simple 6cm nail, sounds loud in any case.

The align and tuning procedure seems very tricky.

Best regards,
Max

[Max]

Hi KT315,
I'm still working on the protoboard version and also in making a thru hole PCB.
Thanks for the useful file. I'm watching for mistakes. Untill now I found only the differences in the reset stage :

- two sources of J113s to ground
- the 470K resistors (motion and autoretune mod) just don't know why R50 should be 10K (seems to me R50 and R49 must be equal - 470K works well on my proto but I prefer motion type detector so I've used a switch to disconnect them both).

and preamp substition (but now it's not the original gs4 here):
- i make the same thing ne5534ap is a really good preamp here

The PCB in the file seems smaller respect to the one I'm designing at now ( this guy -Alex- seems have done a really good reverse on GS-4 and new PCB design).

I had problems with the supply stage (555 voltage doubler) becouse of the noise propagation on the pream section (I'm using NE5534 after a try on different uA709-metallic case revealed they are not really stable --> lot of drift). Think one can use 7660 instead of the old fashioned 70's 555/bjt design.

Also, as indicated by yellow squares, capacitors must be mached in values, becouse of the simmetry of the circuit (I've measured a lot of them before found same values in less than 1% of nominal value). Then also I've used schottky diodes (BAT73) in the supply section and tried them on the timing stage: in supply they improve efficiency but there are no difference in timing stage commutation, now I have 1N4148 on timing that are OK.
Also I've tested TL084 instead of TL064 : are the same in noise level , but more consumption. I think one can use a better LS404 (STmicro) or MC33079(motorola) to have the best here.

I think also the 14.4 batt pack was not a good choice; here one could use maybe an LM2990T-12 (LDO -12 regulator) to use directly a lead acid type battery (say 12V nominal - 1.2 A/h or more) to improve battery life or to maximize peak current on the coil. But I never tested if it works really. Another choice could be a NIMh battery pack (say 15V - 2700ma/h) : I'll try it soon.

In off mode one have the best results in air tests. When switching to GND-balance (all metal mode) performance loss is about 10-15 % in air.
Sel 1 and Sel 2 seems to be operated only if needed and by an expert user to "say" if there is iron or other stuff: just GS4 is not really discriminating , so a big junk of iron, and actually also a simple 6cm nail, sounds loud in any case.

The align and tuning procedure seems very tricky.

Best regards,
Max

[Max]

Hi KT315,
I'm still working on the protoboard version and also in making a thru hole PCB.
Thanks for the useful file. I'm watching for mistakes. Untill now I found only the differences in the reset stage :

- two sources of J113s to ground
- the 470K resistors (motion and autoretune mod) just don't know why R50 should be 10K (seems to me R50 and R49 must be equal - 470K works well on my proto but I prefer motion type detector so I've used a switch to disconnect them both).

and preamp substition (but now it's not the original gs4 here):
- i make the same thing ne5534ap is a really good preamp here

The PCB in the file seems smaller respect to the one I'm designing at now ( this guy -Alex- seems have done a really good reverse on GS-4 and new PCB design).

I had problems with the supply stage (555 voltage doubler) becouse of the noise propagation on the pream section (I'm using NE5534 after a try on different uA709-metallic case revealed they are not really stable --> lot of drift). Think one can use 7660 instead of the old fashioned 70's 555/bjt design.

Also, as indicated by yellow squares, capacitors must be mached in values, becouse of the simmetry of the circuit (I've measured a lot of them before found same values in less than 1% of nominal value). Then also I've used schottky diodes (BAT73) in the supply section and tried them on the timing stage: in supply they improve efficiency but there are no difference in timing stage commutation, now I have 1N4148 on timing that are OK.
Also I've tested TL084 instead of TL064 : are the same in noise level , but more consumption. I think one can use a better LS404 (STmicro) or MC33079(motorola) to have the best here.

I think also the 14.4 batt pack was not a good choice; here one could use maybe an LM2990T-12 (LDO -12 regulator) to use directly a lead acid type battery (say 12V nominal - 1.2 A/h or more) to improve battery life or to maximize peak current on the coil. But I never tested if it works really. Another choice could be a NIMh battery pack (say 15V - 2700ma/h) : I'll try it soon.

In off mode one have the best results in air tests. When switching to GND-balance (all metal mode) performance loss is about 10-15 % in air.
Sel 1 and Sel 2 seems to be operated only if needed and by an expert user to "say" if there is iron or other stuff: just GS4 is not really discriminating , so a big junk of iron, and actually also a simple 6cm nail, sounds loud in any case.

The align and tuning procedure seems very tricky.

Best regards,
Max

[pigeon]

HI MAX


HAVE YOU BUILD GOLDSCAN?HI WORK GOOD?

CAN YOU HELP ME TO MAKE ONE?


THANK YOU

BEST REGARGES


PIGEON