coils for delta pulse

[kt315]

DP works with any type of coil - micro, mini, midi, gyper. for a sens to gold nuggets you may to decrease MAIN SAMPLE DELAY from 40 to 10-15us preset.
you have to tune overdamping resistor more sure carefully also. remember in bulgarian schematic overdamping resistor was 1kOhm.
i will tell about microcoils for DP as find a time.

[rankx0]

I have tried my Delta with coil which works excellent with my Surf PI, but it can't be stabilized - I tried to use potentiometer instead of damping resistor, but it is completely unstable! That one is 280uH.

Then I tried with another coil I made, it is some 810uH / 4.3 Ohm, and it can be damped, DP works stable, but detection is not as good as I expected. I will try to make 400uH coil. Thanks to both of you for your help!

[kt315]

where you bring DP case? if on stomach it will be always unstable. i wrote many times how to shield the case inside
and gave the pics to fix the problem.

[kt315]

I have tried my Delta with coil which works excellent with my Surf PI, but it can't be stabilized - I tried to use potentiometer instead of damping resistor, but it is completely unstable!

you can NOT use ordinary pot directly instead of damping resistor. wrote many times by much people.
ONLY wire-wound pot of big power/watt http://www.directindustry.com/prod/k...85-565843.html
from 4w to more. or diggest of pot and resistors, then you can use ordinary pot connected in parallel spreading main power mainly on a base resistor, 80-90% of
all power, and 10-20% only on the pot.

[rankx0]

I used wire wound trim pot, of course (0.75W). I can't find more power rated pots here

It is not getting warm, so I don't worry about that right now. But I didn't shield the box, it is made of plastic. DP is still on my table, so I thought that shielding won't be necessary at the moment. I will try with shielding, thanks for the advice!

[kt315]

ufff.... i see your knowledge in the electronics is full ZERO ((( BAD!

ordinary low ohms pot is NOT ABLE work in the high voltage circuit. if you open the pot and look you will see
good sparks inside in the slider touch point. WHERE here is sure reliable contact if it is ABSENT!

[kt315]

[kt315]

https://youtu.be/V8EnAJoh3hU?t=1m38s

[rankx0]

Well, perhaps your knowledge of English is close to zero, because I clearly wrote that I DIDN"T USE ORDINARY trim pot, but 0.75W pot. Not wire wound, but 18 turns cermet type http://retam.co.rs/katalog#UG90ZW5ja...y:MTggb2JydGE=.

It doesn't produce sparks and can't be opened, since it is in solid plastic case. And I am pretty sure it can be used for damping purpose, because I tried it and it worked well with Surf PI and works fine with 800uH coil on DP.

[kt315]

my english is perfect if in post #17 you ask about POTENTIOMETER, NOT ABOUT TRIMMER.
and again!!! you write about SURF PI that work with 50us PULSE WIDTH while
DP works with 500us PULSE WIDTH and THE HEATING EMMITED POWER on the resistance is MUCH MORE (look on the title of the thread).
you have to learn electronics buddy. LEARN. while your english is more emotionally rich LOL!

[rankx0]

No need to yell!

[Xtrem]

I have tried my Delta with coil which works excellent with my Surf PI, but it can't be stabilized - I tried to use potentiometer instead of damping resistor, but it is completely unstable! That one is 280uH.

Then I tried with another coil I made, it is some 810uH / 4.3 Ohm, and it can be damped, DP works stable, but detection is not as good as I expected. I will try to make 400uH coil. Thanks to both of you for your help!

If you want to connect a low inductance Coil (280uH), you have to trimm the Delay first, disconnect the collector of VT2 or T2(BC546)
and replace R7(15K) with a 10K ,so you have less delay timing but DELTA going unstable, to make it stable you have to ingrease the PPS tuning the R1 , solder parallel to R1 a 470K Resistor, PPS should be more than 300.at last you have to trimm the PW (about 200uS and less ,is good)

[rankx0]

Thanks a lot! I really don't want to use low inductance coil, just wanted to know why is it unstable - is it a problem with coil, or with DP. Now it is clear that the coil is with too low inductance. I will make 400uH coil and test my DP with that.

[Xtrem]

Ok ,but then the coil (400uH)will be unsuitable for small targets like coins.the problem is DP and Coil.

[rankx0]

No problem, I have Surf PI for small targets.