Minipulse Rev D first attempt

[baum7154]

[QUOTE=Impulse;215530]Hey guys i have gone through each step and all have been a success but i have no depth with my test coil which is a 3dss 8" 0.5mm enamelled copper wire coil
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How many turns of wire is your 8" 3DSS coil? I believe my 8" is 32 turns and measures 334uh. This should give you a benchmark, however mine is wound with 24awg stranded 600 volt PTFE insulated wire which lowers interwire capacitance and raises self resonant frequency.

Perhaps you could post a picture of it.

Good luck,

Dan

[Qiaozhi]

Finally I ordered a MiniPulse kit as a back-up just in case I can't finish my own PI project before the summer.

Do you think it'll work well with a DD coil? Tx is 540uH, 2.8 Ohm; Rx is 13mH, 36 Ohm.

The MPP is designed to work with either a mono or balanced coil. It might be ok with the coil you've specified, but the only real way to find out is to try it.

[Impulse]

You need to use a meter that has an inductance measurement. It's invaluable for this type of work.

For example, with this one you can measure inductance, capacitance, resistance, and transistor hfe. -> http://www.amazon.co.uk/sourcingmap-Multimeter-Resistance-Capacitance-Inductance/dp/B0114KNPV0/ref=sr_1_3?ie=UTF8&qid=1459343416&sr=8-3&keywords=inductance+meter

I have ordered one should be here tomorrow

[Teleno]

Finally I ordered a MiniPulse kit as a back-up just in case I can't finish my own PI project before the summer.

Do you think it'll work well with a DD coil? Tx is 540uH, 2.8 Ohm; Rx is 13mH, 36 Ohm.

[Qiaozhi]

thats my next question how do i use my scope to measure the inductance?

You need to use a meter that has an inductance measurement. It's invaluable for this type of work.

For example, with this one you can measure inductance, capacitance, resistance, and transistor hfe. -> http://www.amazon.co.uk/sourcingmap-Multimeter-Resistance-Capacitance-Inductance/dp/B0114KNPV0/ref=sr_1_3?ie=UTF8&qid=1459343416&sr=8-3&keywords=inductance+meter

[Impulse]

What is the coil inductance?

thats my next question how do i use my scope to measure the inductance?

[Qiaozhi]

the coil is a 3dss 8" (OSD) 0.5mm enameled copper wire.

What is the coil inductance?

[Impulse]

some pics of the board

[Impulse]

could it be the speaker? its a 32 ohm from maplins

http://www.maplin.co.uk/p/025w-mylar-and-paper-round-speaker-45mm-n95fu

[Impulse]

That's a lot lower than it should be.
What are the parameters of the coil?

the coil is a 3dss 8" (OSD) 0.5mm enameled copper wire.

[Qiaozhi]

ok i have tried this and it seems my laptop is the cause! the further the board gets from my laptop the less the erroneous signal presents it self i can only move so far but if get about half a meter away then the signal is nearly gone

so Qiaozhi i take it by "ringing" i am wrong again great! i tried at least!

so for the lack of depth i get my gold ring at about 4"
and a uk £1 at about the same or a little less

That's a lot lower than it should be.
What are the parameters of the coil?

[Impulse]

That's not under damping of the coil. It's external noise pickup. Look at the scope while rotating the coil between vertical and horizontal. You should see the amplitude of the "ringing" change.

ok i have tried this and it seems my laptop is the cause! the further the board gets from my laptop the less the erroneous signal presents it self i can only move so far but if get about half a meter away then the signal is nearly gone

so Qiaozhi i take it by "ringing" i am wrong again great! i tried at least!

so for the lack of depth i get my gold ring at about 4"
and a uk £1 at about the same or a little less

[Qiaozhi]

Hey guys i have taken a trace from tp3 and tp6,

here [ATTACH]35713[/ATTACH]

i can see that the coil i am using is underdamped (i think please tell me if im wrong) from the 'ringing' before and after the pulse on ch1, i have a spare 100k 22 turn pot i can use to get the coil damped correctly i am going to put it in parallel with R1 how do i know that the coil is 'critically' damped? once the ringing is brought to a minimum? eg use the scope on TP3 and Time/div the same but lower the Vertical voltage so i get a better 'zoomed' view of the 'ringing' eg 500mv.

Am i making sence?

That's not under damping of the coil. It's external noise pickup. Look at the scope while rotating the coil between vertical and horizontal. You should see the amplitude of the "ringing" change.

[Impulse]

Does the sample rate change if you change the time/div?

4mhz

8mhz

[green]

It's oscillating all the time so just change the time/div so you still see the oscillation with a different sample rate and see if the oscillation is still 70kHz.