unstable idx

[angleiron]

hi could do with some info on the 100k resistor next to the pinpoint wires on idx pro (pullup resistor i think) saw it on here somewhere cant find it now, is it only to be used with 2 tone because it makes the circuit unstable, im useing a rainbow coil off a eagle sectrum it will detect a pre decimal penny at 35-40 cm with it 10 cm, also i have no descrimination would that be a poor coil match, i have only a multi meter so no test gear have pic of board cant figure how to post got vid though any suggestions would be welcome,thanks

[Koala]

Yes 100K R27 is used with U2 pin 12 to open and close the switch on U2 pin 10-11 to enable disable discrimination channel.

Can't help with your question about your coil never tried one. Don't know if the phase is close enough to allow the Disc to work properly.

[golfnut]

koala is right, if your 100k is not fitted you are stuck in pin pointer mode which is an all metal channel.


fit the 100k and your switch will allow the disc ch to work

you will be able to swipe the target from side to side then also rather then bobbing.


ditch the black sounder, with respect they are not good, put headphones or a small speaker in there

[angleiron]

thanks for the advice soldered the resistor back in very eratic cant get a tone, then starts to oscilate when i turn up the disc trouble there is no component numbers just values it is late 2013 silverdog board, i think i have read somewhere if the leads to the pots are too long it upsets the board, have taken pics dont know how to attach says no permission,will have to make a coil see if it is that

[Koala]

thanks for the advice soldered the resistor back in very eratic cant get a tone, then starts to oscilate when i turn up the disc trouble there is no component numbers just values it is late 2013 silverdog board, i think i have read somewhere if the leads to the pots are too long it upsets the board, have taken pics dont know how to attach says no permission,will have to make a coil see if it is that[ATTACH]31419[/ATTACH][ATTACH]31420[/ATTACH]

Coil is working fine in All metal mode so should be stable in Disc mode if the phase is too far out the disc will be out of range.

Now you have put the 100K if you short the PP connector does it work as before.

Guess your voltages are okay as PP mode works well but worth checking

A good start is to measure all the resistors with a meter. Pay attention to the value i.e. you've not put a 100 ohm instead of 100K we have all done it. All the resistor measure correct in circuit except for a couple around the PSU which measure half what they should. Its a good way to eliminate a lot of components.

Look around your sockets its very easy for a pin to bend under instead into the socket especially U2

[golfnut]

To see if your machine is built well and to eliminate you coil suitabilty.


Remove the Rx coil wires from your PCB.

Add a 2k2 or a 3k3 or 4k7 across the PCB RX coil terminals.


In this case your Tx will run ok, the Rx chain should sit quietly without any drama. If it behaves like this it points to the coil suitability for this project.


Another thing, sorry dont mean to offend, Do you know you have the Rx coil on the RX and Tx coil on the Tx oscillator???

[Koala]

Video of the problem might help.

Does the ground balance work correctly

[angleiron]

hi koala and golfnut, no by no means will you offend me i have little expertees in electronics, just a chancer so the coil could be wrong, i have based it on the xlt coil i think the eagle spectrum was its predecessor the coil has damaged ears but works fine not had chance to check all components nor the 3k3 resistor, does that mean i leave the coil connected and dissconect the rx and solder the resistor across the rx done a vid + pics see if i can up it, thanks both of you for your time

[Koala]

hi koala and golfnut, no by no means will you offend me i have little expertees in electronics, just a chancer so the coil could be wrong, i have based it on the xlt coil i think the eagle spectrum was its predecessor the coil has damaged ears but works fine not had chance to check all components nor the 3k3 resistor, does that mean i leave the coil connected and dissconect the rx and solder the resistor across the rx done a vid + pics see if i can up it, thanks both of you for your time[ATTACH]31429[/ATTACH][ATTACH]31430[/ATTACH][ATTACH]31431[/ATTACH][ATTACH]31432[/ATTACH]

I don't know the wiring of the the Spectrum coil but the the two RX connections should have a higher resistance than the TX connections.

Is your threshold working? Can't tell from the video. Turned one way should go quite and then gradually increase as you turn the POT. Best results are when the hum is very faint.

Ground balance can on be checked in pin point mode. You need to set the threshold to a very faint hum and wave a small piece of ferrite a few inches in front of the coil while adjusting the ground balance. You should be able to reject the ferrite so the hum stay the same as the ferrite is waved in front of the coil. If you can get this to work there is a good chance the coil will be usable.

Ferrite can sometimes found on the end of cables (mobile phone and USB that have a bulge at on end) old LW radios aerials. The ring type that are in PSUs don't work too well but fine if you break it and use a piece of it.

[Koala]

"dissconect the rx and solder the resistor across the rx" = yes

[golfnut]

I think you have a chance here, but to be fair boss those leads to the pots may be a small part of your issue.

Try to make all the pot leads the length thy would be in a metal detector.

The GeB pot leads were the most twitchy on my one.

Twisting the pot wires can help.

I needed to add a screen to one of my pot wires on one of my kits.



Also loose the black sounder. your results will sound crap. A small speaker is better, like on a real detector. Andy - Silverdog only puts these in as a bit of a freebie and I dont recommend them.

I would move the coil away from yous pcb more so your not transmitting up itself.

I have had some intability with these on and off - the rate they normally go at is about 8Hz , where there is masses of gain in the filter amps.

So they chatter at 8Hz. Yous is going at about 1 or 2 Hz cant say what that is.


Part of the problem is everybodys physical build differs, so all bets are off for repeatable performance.

Also almost every build has a different coil and Rx initial phasing



A guy recently did a board with the pots along the edge, like a real detector, this is the format of board that will get all builders further and faster.

It may be that the Rx front end is co tuned with the Tx and somehow beating.

Without a scope or a little more knowledge it can be a pain. Some use a pc scope

You want about 16Vpp Tx at about 6.5kHz

The Rx preamp output level ~300mV or less no more.

Need to first be able to reject ferrite using geb, hopfully mid travel.

If you cant do that your wasting time. The Rx initial phase has to be right for this and subsequent corrct operation.


I had never used a detector before and built the IGSL and although it worked was a head F to get it all going without a scope etc.

[angleiron]

thanks for the reply

[angleiron]

thanks golfnut and koala for the replies had a look at the coil again and swapped around some wires i suppose the start and finish of the rx and tx coils are important . so all done tried it out and got discrimination and tuning, tone working as, should but very deaf only detect a pre decimal penny at about 2 inches possibly the coil is not compatible, always thought the blue max coil was compatible with the whites eagle spectrum so i thought vica versa, if i get chance this w end will try to wind a coil and give it a test again thanks for your time