Just started MPP project

[green]

Thanks Green. That makes a difference. I might note that I can get nowhere near 1us/DIV.

Hi multieagle. Thanks for trying. My error on the channel 2 scale, should set 50 volts/div with scale and probe at x10. I don't understand the time scale, maybe someone could explain. Be sure the probe is x10 when looking at coil volts.

[Chet]

Hi multieagle


Your scope works by collecting thousands of samples during many repetitive cycles of the waveform that you are trying to observe. If your sweep speed is set at 100 us/division then at a 1 MHz sample rate it is collecting 100 samples X ten divisions = 1000 samples each time the sweep is triggered. These are stored in memory and sweeps are processed by software to reconstruct many of these sample periods into a waveform for display.


Expensive oscilloscopes use a similar method but many of them sample at 1 gigahertz or higher rates.


One problem with a slow 1 MHz sample rate is the signal being observed must be very stable in amplitude and voltage triggering points. If not the software processing cannot align the starting points of each sweep. This results in a choppy distorted reproduction of the waveform.


If the waveform is a very stable sinewave or square wave 1 MHz sample rate works quite well and a very clean display is created.


The waveform from the flyback pulse varies some in firing point and amplitude from pulse to pulse and it is a very short narrow event. This changes the triggering points/starting points slightly. This creates some problem for the software to reconstruct good fidelity of the flyback or the receiver signals.


TP1 is the best reference pulse for processing. The best setup is to always have TP1 on channel 1 and trigger on TP1/channel 1. Then view the TP of interest on channel 2.


The video that you made looks like TP1 may not have been triggered correctly. The trigger point (yellow T arrow) should be adjusted to be half way up on the amplitude of pulse from TP1.


The previous screen shot that you posted with the settings from green wasn’t that bad. Try a few more times paying close attention to the triggering level. And try again to get to a faster horizontal sweep speed of 50, 20, 10, or 5 usec.


Regards,
Chet

[Chet]

I can pick this up locally for C$150 http://www.amazon.com/Elenco-Oscillo.../dp/B0002EWO3K Is it a decent buy?

Hi multieagle

If this scope is in good working order it is a good buy. But if you can get your existing scope working better you may not need to spend the money for something that you may not use often.

Regards,
Chet

[multieagle]

Thanks folks! Starting to understand a tad more each day. Here is the latest image with CH1 on TP1 and CH2 on outer leg of R3. Am able to use 50us and 5v on both channels. Is this still indicative of a problem at U2? Additional note: Rise time switches between 1 - 2 uS, Fall Time stable on 1uS. Max/Min = 914mV & (-)1.4V

[green]

Thanks folks! Starting to understand a tad more each day. Here is the latest image with CH1 on TP1 and CH2 on outer leg of R3. Am able to use 50us and 5v on both channels. Is this still indicative of a problem at U2? Additional note: Rise time switches between 1 - 2 uS, Fall Time stable on 1uS. Max/Min = 914mV & (-)1.4V

Hi multieagle. I'm not seeing the trigger position indicator at the top of the screen. Set channel 1 scale and probe to x1, 5 volts/div. Set channel 2 display and probe to x10 and 50 volts/div Set trigger to edge, normal, ch1,- slope. Looking at the manual sometimes the trigger indicator is there sometimes not. In the manual the indicator is half way across the screen. It seems like you should be able to move it, but I don't see where. My scope, the indicator can move off screen if it isn't centered when switching to shorter times/div.(example 100usec/div to 10usec/div). Reply #64, Ch1 slope change isn't in the center and there isn't a trigger indicator on the screen. I think understanding the trigger might be the answer.

[multieagle]

Hi multieagle. I'm not seeing the trigger position indicator at the top of the screen. Set channel 1 scale and probe to x1, 5 volts/div. Set channel 2 display and probe to x10 and 50 volts/div Set trigger to edge, normal, ch1,- slope. Looking at the manual sometimes the trigger indicator is there sometimes not. In the manual the indicator is half way across the screen. It seems like you should be able to move it, but I don't see where. My scope, the indicator can move off screen if it isn't centered when switching to shorter times/div.(example 100usec/div to 10usec/div). Reply #64, Ch1 slope change isn't in the center and there isn't a trigger indicator on the screen. I think understanding the trigger might be the answer.

Well, something is working after a bit of fidgiting. When I place a popcan on the coil, the trace moves two divisions to the left. Images attached. Great having personal tutors! Thanks again fellows.

[green]

Well, something is working after a bit of fidgiting. When I place a popcan on the coil, the trace moves two divisions to the left. Images attached. Great having personal tutors! Thanks again fellows.

Hi multieagle. Looks like Ch1 probe x10 not x1, Ch 2 probe x1 not x10, trigger +(rising) not -(falling). Is trigger normal or auto? I think you should be able to look at flyback at 1 or 2 usec/div if can get trigger right, maybe not. Don't know why the shift when looking at the can.

[Chet]

Hi multieagle

I agree with green it looks like the sweep is not being triggered at a constant level. Can you move the two traces apart vertically so that the upper part of the flyback pulse is not crossing above channel 1. Then using channel 1 for the trigger source slowly adjust the trigger level to get the best stable display.

Regards,
Chet

[multieagle]

Hi multieagle. Looks like Ch1 probe x10 not x1, Ch 2 probe x1 not x10, trigger +(rising) not -(falling). Is trigger normal or auto? I think you should be able to look at flyback at 1 or 2 usec/div if can get trigger right, maybe not. Don't know why the shift when looking at the can.

Thanks for sticking in there, green. The attached images show settings as per your instructions and where they must be on the Hantek to get a meaningful signal.
The popcan is now registering differently. I'm getting movement on CH2 (R3) as follows: with popcan on coil: 151-529 Hz .... Popcan removed: 1.057KHz. I would assume this is shouting at me, "Signal is correct at R3, but something is wrong at TP1????" Does that make sense? So, are we back to a faulty U2?

[Chet]

Hi multieagle

U2 will not effect TP1 or the flyback pulse. It looks like you have a bad connection on TP1 or a bad probe. Try changing probes or put both probes on TP1 and see if they work the same. Otherwise maybe the channel 1 input to your oscilloscope has gone bad.

Chet

[multieagle]

Hi multieagle

U2 will not effect TP1 or the flyback pulse. It looks like you have a bad connection on TP1 or a bad probe. Try changing probes or put both probes on TP1 and see if they work the same. Otherwise maybe the channel 1 input to your oscilloscope has gone bad.

Chet

Well Chet, do not know what happened, but when I switched probe locations, and hit AUTO, both worked perfectly (I think). Frequency now pulses between 530Hz - 1.059KHz. See attached. Also image both Channels at 5V.

[Chet]

The signals are back but the voltages are wrong. Do your test probes have a label on them that says whether they are X1 or X10? See if you can now go to a faster sweep of 50 us or less.

The frequency 1.059 KHz is correct; the 530 Hz is some kind of noise or signal distortion that is causing a false frequency reading. A can near the coil cannot effect the pulse rate of the 555 oscillator which is designed to pulse at a 1KHz rate.

Chet

[multieagle]

The 530Hz appears only when the can is on or near the coil. Otherwise it is steady on 1.059KHz. So as far as I can tell, the can is the source of the drain.

Gord

[multieagle]

The signals are back but the voltages are wrong. Do your test probes have a label on them that says whether they are X1 or X10? See if you can now go to a faster sweep of 50 us or less.

The frequency 1.059 KHz is correct; the 530 Hz is some kind of noise or signal distortion that is causing a false frequency reading. A can near the coil cannot effect the pulse rate of the 555 oscillator which is designed to pulse at a 1KHz rate.

Chet

I have CH1 attached to R3, and CH2 to TP1. I assume CH1 (R3) is causing the reaction to the can???? Here is a larger image at 50us and 2v each channel. I am steady at 1.06v which decreases when can is placed on coil. So must assume the can is causing the drain. Both CH1 & CH2 traces move approx. 2 divisions to the left (facing) when the can is on the coil. And when passed back and forth over the coil the trace also moves back and forth. If I go to 1v both channel traces disappear at 50us.

[green]

multieagle, connect both probes to a battery(9v or 12v) scope (5volts/div x1, probes x1) and (scope 5volts/div x1, probes x10). See if the traces show battery volts with probes x1 and .1x battery volts with probes x10.