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Author Topic: Lidmotor's Penny circuit help needed.  (Read 52561 times)

Dark Alchemist

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Re: Lidmotor's Penny circuit help needed.
« Reply #30 on: September 28, 2013, 10:15:24 PM »
1us

Dark Alchemist

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Re: Lidmotor's Penny circuit help needed.
« Reply #31 on: September 28, 2013, 10:15:41 PM »
10us

Dark Alchemist

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Re: Lidmotor's Penny circuit help needed.
« Reply #32 on: September 28, 2013, 10:15:56 PM »
50us

Dark Alchemist

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Re: Lidmotor's Penny circuit help needed.
« Reply #33 on: September 28, 2013, 10:16:10 PM »
100us

TinselKoala

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Re: Lidmotor's Penny circuit help needed.
« Reply #34 on: September 29, 2013, 01:42:28 AM »
Weird. Thanks for doing that, even though it leaves me a bit more confused about what is going on.
The _average_ value of that oscillation is at your 0.5 volt supply voltage, and the peaks never seem to go high enough to overcome the LED's forward voltage. So this signal could not be lighting up the LEDs, especially not 4 in series.

Could you please try this now: Set your trigger voltage to some value decently _above_ the peaks shown in the traces above. Try setting the trigger to +2.0 V, and the timebase back to 1 millisecond per division, and wait a bit to see if anything shows up.  What I am thinking is that perhaps your circuit is oscillating in bursts and we are missing the voltage peak that lights the LEDs.

I've rewired my JT testbed to correspond to the circuit in your schematic, except that my inductance is still a bit low and I don't have the right transistor. But with 2n2222 I get this: the circuit flashes both the single LED or the 24-LED 2series-12parallel array at about 1 per second. The flashes are fairly dim. If I use the MPSA18 the flash rate increases to perhaps 2 per second. I've got a bunch of low-voltage "dead" batteries and I found one that indicates 0.7 V open-circuit, and this battery powers the circuit fine, but another one with under 0.4 volts won't. I don't have an easy way to provide a precise 0.5 volts supply at the moment, but later on tonight I'll try to make one.

Now, I've just used the "single shot" capability of my Link DSO to capture the waveform of a single flash. It's pretty interesting.




TinselKoala

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Re: Lidmotor's Penny circuit help needed.
« Reply #35 on: September 29, 2013, 02:02:11 AM »
I've made a video of what I'm talking about, but it will be a few minutes before it's processed and uploaded. Check this space in a few minutes for the link.

Dark Alchemist

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Re: Lidmotor's Penny circuit help needed.
« Reply #36 on: September 29, 2013, 02:05:38 AM »
I think something is seriously wrong with Spice as I did what you said and set it to single and 2.0V trigger level.  Nothing happened then I got a big burst and nothing but as the nothing was happening after that burst my LEDs were flashing.

The burst is almost 1000us long then nothing but the LEDs are flashing.  So, that means the voltage never goes over 2 volts to trigger the scope but those 3.45v LEDs are all flashing.

So, what gives, or basically WaTaF is going on with this simulation?

TinselKoala

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Re: Lidmotor's Penny circuit help needed.
« Reply #37 on: September 29, 2013, 02:29:13 AM »
I think something is seriously wrong with Spice as I did what you said and set it to single and 2.0V trigger level.  Nothing happened then I got a big burst and nothing but as the nothing was happening after that burst my LEDs were flashing.

What gives?

Nothing is wrong, your circuit is doing just exactly what I thought, and mine is doing the same thing, I think. I'm uploading a video explanation right now, showing how to catch the oscillation bursts. It should be up in half an hour or so, my upload connection is really slow.

http://youtu.be/9FDmkbCbKP0


TinselKoala

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Re: Lidmotor's Penny circuit help needed.
« Reply #38 on: September 29, 2013, 02:34:43 AM »
I think something is seriously wrong with Spice as I did what you said and set it to single and 2.0V trigger level.  Nothing happened then I got a big burst and nothing but as the nothing was happening after that burst my LEDs were flashing.

The burst is almost 1000us long then nothing but the LEDs are flashing.  So, that means the voltage never goes over 2 volts to trigger the scope but those 3.45v LEDs are all flashing.

So, what gives, or basically WaTaF is going on with this simulation?

Sorry, we crossed posts there. The Single Shot mode does one sweep after it's triggered, then you have to restart or repress Single Shot for another triggered sweep. So you captured a single sweep, probably, and then the scope stopped. Your circuit is still running and for sure there must be spikes in there that exceed the combined fwd voltage of the LED string, or they would not light.
It might be clearer when you watch my video. I _think_ I've captured the behaviour, but since I'm using a different transistor I can't yet be sure, until we are both showing similar scopeshots. We do seem to be making some progress, though!

Dark Alchemist

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Re: Lidmotor's Penny circuit help needed.
« Reply #39 on: September 29, 2013, 02:46:52 AM »
I will watch it once it is up but what I did was set it to single shot 3.4V (LEDs are 3.45v) and it never ever triggered BUT the LEDs were flashing like mad.

It triggers at a max of 2.25V

TinselKoala

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Re: Lidmotor's Penny circuit help needed.
« Reply #40 on: September 29, 2013, 03:02:45 AM »
Weird.
Anyhow, the video is ready now.
http://www.youtube.com/watch?v=9FDmkbCbKP0

Legalizeshemp420

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Re: Lidmotor's Penny circuit help needed.
« Reply #41 on: September 29, 2013, 03:03:28 AM »
I decided to unify my old account and make this account since Youtube knows me as someone else (this name) and Dark Alchemist was taken over there.

I figure I will be doing a lot of work like this and need to have the names of both places the same.

Dark Alchemist

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Re: Lidmotor's Penny circuit help needed.
« Reply #42 on: September 29, 2013, 03:05:58 AM »
I just posted under my new account here of the name I go by on Youtube.  This name was taken over there so I had to use something else.  I figure I need the same name here and there since I plan on doing a lot of work with this stuff and my 20mhz scope was shipped today (100mhz DSO will be sometime next year Rigol 1152E I think).

My new post is above this one but needs moderator approval before it shows.

Dark Alchemist

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Re: Lidmotor's Penny circuit help needed.
« Reply #43 on: September 29, 2013, 03:21:53 AM »
Here is a weird oddity and that is at 0.5V max trigger is 2.25V at 1.4V it becomes 6.715V

TinselKoala

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Re: Lidmotor's Penny circuit help needed.
« Reply #44 on: September 29, 2013, 05:12:23 AM »
Well, is my circuit behaving like yours yet? Were you able to get similar scopeshots of the bursts to what I was getting?