Minipulse Rev D first attempt

[Impulse]

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

yes it does but then most if not all of the sample is off screen, i can try the same test points with different time/div?

[green]

hey green if you are asking me to change the scope frequency then this i cannot do as my pc scope does not allow it.

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

[Impulse]

My guess. It's not damping. Try changing sample rate to see if you are aliasing on a higher frequency. See if oscillation stays at 70kHz.

hey green if you are asking me to change the scope frequency then this i cannot do as my pc scope does not allow it.

[green]

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?

My guess. It's not damping. Try changing sample rate to see if you are aliasing on a higher frequency. See if oscillation stays at 70kHz.

[Impulse]

ok i tried the above and nothing changed i also tried the 100k 22turn in series this also didnt work.

[Impulse]

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

here

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?

[Qiaozhi]

ok so the preamp output is to the coil? TXRX

if so [ATTACH]35698[/ATTACH]

and main sample pulse width is 48us

[ATTACH]35699[/ATTACH]

Not quite.
The preamp output is at TP3 (U5 pin7). What we need to see is a comparison between the signal at TP3 (CH1) and the main sample pulse at TP6 (CH2).
Both signals need to displayed in the same image. Set the scope to trigger on CH1.

[Impulse]

Probe the preamp output on channel 1, and the main sample pulse on channel 2. This will confirm whether you have the main sample pulse set correctly.
Also check you have the optimum value for the damping resistor.

ok so the preamp output is to the coil? TXRX

if so

and main sample pulse width is 48us

[Qiaozhi]

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

step6 i have set the sample delay to 22us
[ATTACH]35697[/ATTACH]

step7 i used my multi meter and i got a large votage swing when i introduce a can to the coil from 500mV to 4vdc

step8 worked as described the SAT worked fine a little slow though

step9 the VCO works fine i am using a 32 ohm speaker (small)

i have tried a new coil also, which is a 10" 0.5mm insulated wire coil 24turns with both of the coils i get about 3" at the most with a usa quarter. any ideas guys?

Probe the preamp output on channel 1, and the main sample pulse on channel 2. This will confirm whether you have the main sample pulse set correctly.
Also check you have the optimum value for the damping resistor.

[Impulse]

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

step6 i have set the sample delay to 22us


step7 i used my multi meter and i got a large votage swing when i introduce a can to the coil from 500mV to 4vdc

step8 worked as described the SAT worked fine a little slow though

step9 the VCO works fine i am using a 32 ohm speaker (small)

i have tried a new coil also, which is a 10" 0.5mm insulated wire coil 24turns with both of the coils i get about 3" at the most with a usa quarter. any ideas guys?

[Impulse]

ok step 5 at tp3 i used my multi meter and got 11.6vdc and used a can of soup (only thing a had large enough) and the voltage droppped to 11.53vdc seems like all is ok.

[Impulse]

My scope cannot handle more than 80v in 10x I don't want to break it . Thanks Qiaozhi for you help again

[Qiaozhi]

Hey guys does the scope image look rite I don't want to move on without confirming that it is correct?

Your PC scope appears to be limiting the amplitude so that you're not seeing the full flyback voltage. Try changing the setting on CH1 from x1 to x10, and use a x10 probe.
However, since you can actually hear the TX oscillator in the headphones, it's most likely ok for you to carry on.

[Impulse]

Hey guys does the scope image look rite I don't want to move on without confirming that it is correct?

[Impulse]

ok ignore the last 3 posts i have my head on now!! i have TX RX connected to the inner most winding and pin 3 of PL2 to the outer most winding now this is the o-scope image i get

here

and i now get the tone in the headphones yay!