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Author Topic: Lidmotor's Penny circuit help needed.  (Read 52570 times)

TinselKoala

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Re: Lidmotor's Penny circuit help needed.
« Reply #90 on: October 03, 2013, 03:34:13 AM »
I just tried 2n2222 and it behaves the same, but with slightly less voltages.
Still using the same battery, and with the 2n2222 in there with collector and base swapped, the battery voltage is 382 mV.
With the 2n2222 the correct way round, the battery voltage is back to 358 mV.

And changing back to the MPSA18, battery voltage drops to 333 mV again. So the 2n2222 isn't letting as much current through it, and the battery isn't sagging as much when the 2n2222 is used. Collector peaks smaller too.



Legalizeshemp420

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Re: Lidmotor's Penny circuit help needed.
« Reply #91 on: October 03, 2013, 03:35:01 AM »
MPSA18

Legalizeshemp420

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Re: Lidmotor's Penny circuit help needed.
« Reply #92 on: October 03, 2013, 03:50:33 AM »
MPSA18 without the cap.  Notice Channel B and its settings.

TinselKoala

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Re: Lidmotor's Penny circuit help needed.
« Reply #93 on: October 03, 2013, 03:51:38 AM »
That's strange. I am using the same circuit, except without the 1.2 nF cap, and my MPSA18 keeps the 4 series LEDs lit down to a supply voltage of 0.650 volts, about, and at 1.4 volts (from DC regulated supply) the LEDs are brilliant.



TinselKoala

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Re: Lidmotor's Penny circuit help needed.
« Reply #94 on: October 03, 2013, 04:02:17 AM »
You just made me check again. I wanted to make sure I had the MPSA18 in there! And it is.
I warmed the battery using the soldering iron to raise the voltage, and the LEDs come on visibly at a battery voltage of 0.610 volts.

Legalizeshemp420

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Re: Lidmotor's Penny circuit help needed.
« Reply #95 on: October 03, 2013, 04:07:43 AM »
You just made me check again. I wanted to make sure I had the MPSA18 in there! And it is.
I warmed the battery using the soldering iron to raise the voltage, and the LEDs come on visibly at a battery voltage of 0.610 volts.
Well, SPICE is not going to do it.  It could be anything causing it not to do a real world scenario but when you have over 30 different items you can adjust per simulation run there is just too much to handle.

This is making me despise simulations because there are some oddities that they can't simulate.  Sort of like a Tricorder from Star-Trek or that transistor identifier that doesn't know what something is until it sees it first, or is entered.  I am sure I could eventually get it to mimic real life but to what end and how many decades do I have to modify all of the data to get it to do it?  It is not something as simple as changing 1 parameter because when you change 1 another might have to be changed or it will error out.  Too many variables for me.

Legalizeshemp420

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Re: Lidmotor's Penny circuit help needed.
« Reply #96 on: October 03, 2013, 04:12:05 AM »
Here is one for you.  0.7V backwards MPSA18 and the probe is on the base and the ground (the ground is hidden below the LEDs but always remember it is there).

TinselKoala

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Re: Lidmotor's Penny circuit help needed.
« Reply #97 on: October 03, 2013, 04:52:36 AM »
Well, that's strange. I'd like to see that expanded, it looks like a single classical inductive ringdown envelope. Again, I'm not convinced you've captured a whole cycle yet there.

One issue might be the LEDs. I am using superbright blues, but I don't know the part number or manufacturer. My Fluke 83 DMM reports the forward voltage as 2.6 volts and the LED draws 220 microAmps at that voltage... and is already fairly bright. (Microammeter in series with the Fluke, with the Fluke in diode check mode.)

When supplied with a regulated DC supply (HP721A) the diode begins to glow visibly at 2.295 V and a current of 1 microamp! To put 20 milliAmp through it I need to go to 3.5 volts and the LED is blindingly brilliant.

Legalizeshemp420

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Re: Lidmotor's Penny circuit help needed.
« Reply #98 on: October 03, 2013, 04:58:47 AM »
Yes, it does look like that doesn't it?  This LED (I tried to make another and it never worked) is a BLUE LED
Vf = 3.45V @ 20mA but I am not certain about that because every LED says GENERIC / LED_RED so obviously National just did a C&P job.

I am about to put up the video of it on Youtube so I will post back in a bit.

Legalizeshemp420

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Re: Lidmotor's Penny circuit help needed.
« Reply #99 on: October 03, 2013, 05:15:43 AM »
www.youtube.com/watch?v=7XlXCnY5bZY

You know I wonder if what is causing your continual oscillation could be because the circuit is actually inside the toroid and it is somehow having a case of feedback however minimal?

TinselKoala

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Re: Lidmotor's Penny circuit help needed.
« Reply #100 on: October 03, 2013, 07:24:35 AM »
I don't know how to interpret what you are showing on the scope. You may have to go back to the single-shot search like I showed before, until you have a setting that displays a whole period in one screen, without clipping voltage.

It sounds like your LED model is quite close to what I'm actually getting with these LEDs. How does your sim tell you the LEDs are shining? I mean does it light up the symbol or what?

I don't think the circuit being inside the toroid makes a difference but it's easy enough to check... if this battery ever runs down, I'll separate out the board from the toroid and test again. Since I heated the battery up, it's back up to over 340 mV again... actually just now went down to 339 mV. Still oscillating at 492.3 kHz, with 1420  mV peaks.

Legalizeshemp420

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Re: Lidmotor's Penny circuit help needed.
« Reply #101 on: October 03, 2013, 07:36:44 AM »
Those little arrow symbols on the LED light up with the color of the LED being tested.


Legalizeshemp420

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Re: Lidmotor's Penny circuit help needed.
« Reply #102 on: October 03, 2013, 07:43:09 AM »
MPSA18 backwards.

TinselKoala

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Re: Lidmotor's Penny circuit help needed.
« Reply #103 on: October 03, 2013, 07:55:09 AM »
OK.... that's the envelope of the single pulse. It doesn't repeat this, it just does it one time when you apply power?

I can see that there is more power dissipated in the MPSA18 than in the BC337, certainly. But why don't our waveforms look more similar? I'm pretty burned out tonight, I've been working all afternoon, but I'll do some more testing after I've had some shut-eye.

Sometimes JT circuits need to be kicked into oscillation. You could try putting momentary-contact switches between base and emitter, and between base and collector. Punching the switch for a few microseconds or a millisecond might work. At least the real hardware often works like this, even with big JTs using 2n3055s.


ETA: Can you move your trigger point over to the right a bit? You have it at the leftmost edge of the screen, and this prevents you from seeing what happens in the "pretrigger" time. In most of the shots I've shown, my trigger is set horizontally at screen center.  Try dragging the triangular icon at the top left of the screen, over to the third or fourth horizontal division.

Legalizeshemp420

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Re: Lidmotor's Penny circuit help needed.
« Reply #104 on: October 03, 2013, 08:01:45 AM »
OK.... that's the envelope of the single pulse. It doesn't repeat this, it just does it one time when you apply power?

I can see that there is more power dissipated in the MPSA18 than in the BC337, certainly. But why don't our waveforms look more similar? I'm pretty burned out tonight, I've been working all afternoon, but I'll do some more testing after I've had some shut-eye.

Sometimes JT circuits need to be kicked into oscillation. You could try putting momentary-contact switches between base and emitter, and between base and collector. Punching the switch for a few microseconds or a millisecond might work. At least the real hardware often works like this, even with big JTs using 2n3055s.


ETA: Can you move your trigger point over to the right a bit? You have it at the leftmost edge of the screen, and this prevents you from seeing what happens in the "pretrigger" time. In most of the shots I've shown, my trigger is set horizontally at screen center.  Try dragging the triangular icon at the top left of the screen, over to the third or fourth horizontal division.
Dragging them has no effect because, unlike a real scope, moving those llines neither increments nor decrements anything.  Sort of worthless in that respect and they don't hide anything either.

WOW, I can't explain it but the kicking worked.  It increased the current it was giving by a LOT too.