how does this flasher stand up in the long haul!

Does that actually flash? With just a 5 volt supply?

John

Reply to
John Larkin
Loading thread data ...
470 5 VOLTS ___ -|___|-+----------+ | | | | | + 2N2222 | | - | | | | === === GND GND

Jamie

Reply to
Jamie

no it does not, I just through some values at it, I just wanted opinions about zenering the emitter. normally you would use at least 10volts or more..

I always thought avalanching the (BE) wasn't a very good idea.

Jamie

Reply to
Jamie

T24gT2N0IDksIDE6MTmgYW0sIEphbWllCjxqYW1pZV9rYTFscGFfbm90X3ZhbGlkX2FmdGVyX2th MWwuLi5AY2hhcnRlci5uZXQ+IHdyb3RlOgo+IEpvaG4gTGFya2luIHdyb3RlOgo+ID4gT24gU2F0 LCAwOCBPY3QgMjAxMSAxODoyNToxNCAtMDQwMCwgSmFtaWUKPiA+IDxqYW1pZV9rYTFscGFfbm90 X3ZhbGlkX2FmdGVyX2thMWwuLi5AY2hhcnRlci5uZXQ+IHdyb3RlOgo+Cj4gPj4goCCgIKAgoCCg IKAgoCCgNDcwCj4KPiA+PiCgIDUgVk9MVFMgoCCgIKAgX19fCj4gPj4goCCgIKAgoCCgIKAgoCAt fF9fX3wtKy0tLS0tLS0tLS0rCj4gPj4goCCgIKAgoCCgIKAgoCCgIKAgoCCgfCCgIKAgoCCgIKB8 Cj4gPj4goCCgIKAgoCCgIKAgoCCgIKAgoCCgfCCgIKAgoCCgIKB8Cj4gPj4goCCgIKAgoCCgIKAg oCCgIKAgoCCgfCCgIKAgoCCgIKArIKAgoCAyTjIyMjIKPiA+PiCgIKAgoCCgIKAgoCCgIKAgoCCg IKB8IKAgoCCgIKAgoCA8fAo+ID4+IKAgoCCgIKAgoCCgIKAgoCCgIKAgoCsgoCCgIKAgoCCgIKB8 LQo+ID4+IKAgoCCgIKAgoCCgIKAgoCCgIKAgoHwgoCCgIKAgoCCgIC98Cj4gPj4goCCgIKAgoCCg IKAgoCCgIKAgoCAtLS0goCCgIKAgoCB8Cj4gPj4goCCgIKAgoCCgIDEwMDAgdWYgoCAtLS0goCCg IKAgoCB8Cj4gPj4goCCgIKAgoCCgIKAgoCCgIKAgoCCgKyCgIKAgoCCgIC4tLgo+ID4+IKAgoCCg IKAgoCCgIKAgoCCgIKAgoHwgoCCgIKAgoCB8IHwKPiA+PiCgIKAgoCCgIKAgoCCgIKAgoCCgIKB8 IKAgoCCgIKAgfCB8IKAgMTIwCj4gPj4goCCgIKAgoCCgIKAgoCCgIKAgoCCgfCCgIKAgoCCgICct Jwo+ID4+IKAgoCCgIKAgoCCgIKAgoCCgIKAgoHwgoCCgIKAgoCCgfAo+ID4+IKAgoCCgIKAgoCCg IKAgoCCgIKAgoHwgoCCgIKAgoCCgfAo+ID4+IKAgoCCgIKAgoCCgIKAgoCCgIKAgoHwgoCCgIKAg oCCgViAtPgo+ID4+IKAgoCCgIKAgoCCgIKAgoCCgIKAgoHwgoCCgIKAgoCCgLQo+ID4+IKAgoCCg IKAgoCCgIKAgoCCgIKAgoHwgoCCgIKAgoCCgfAo+ID4+IKAgoCCgIKAgoCCgIKAgoCCgIKAgoCB8 IKAgoCCgIKAgfAo+ID4+IKAgoCCgIKAgoCCgIKAgoCCgIKAgoD09PSCgIKAgoCA9PT0KPiA+PiCg IKAgoCCgIKAgoCCgIKAgoCCgIKBHTkQgoCCgIKAgR05ECj4KPiA+PkphbWllCj4KPiA+IERvZXMg dGhhdCBhY3R1YWxseSBmbGFzaD8gV2l0aCBqdXN0IGEgNSB2b2x0IHN1cHBseT8KPgo+ID4gSm9o bgo+Cj4gbm8gaXQgZG9lcyBub3QsIEkganVzdCB0aHJvdWdoIHNvbWUgdmFsdWVzIGF0IGl0LCBJ IGp1c3Qgd2FudGVkIG9waW5pb25zCj4gYWJvdXQgemVuZXJpbmcgdGhlIGVtaXR0ZXIuIG5vcm1h bGx5IHlvdSB3b3VsZCB1c2UgYXQgbGVhc3QgMTB2b2x0cyBvcgo+IG1vcmUuLgo+Cj4goCCgSSBh bHdheXMgdGhvdWdodCBhdmFsYW5jaGluZyB0aGUgKEJFKSB3YXNuJ3QgYSB2ZXJ5IGdvb2QgaWRl YS4KPgo+IEphbWllCgpBbiBTQ1Igc2hvdWxkIHdvcmssIG9yIDIgdHJzIGNvbm5lY3RlZCB0byBt YWtlIGFuIHNjcgoKCk5UCg==

Reply to
NT

yes, but this will unlatch and flash for you.

This circuit is very simply. I was just curious as to longevity of the transistor in such a configuration.

Jamie

Reply to
Jamie

--
How so? with the base connected to air all you've got is two diodes in
series opposition.
 Click to see the full signature
Reply to
John Fields

It's a transistor negative-resistance effect that Spice apparently doesn't model.

formatting link

formatting link

In your sim, you have 23 volts base-emitter, so the Spice model is very wrong.

John

Reply to
John Larkin

formatting link

Yeah. I ran into this before when I tried to use the e-b junction as a zener. AFAIK, LTSpice does not model Veb at all.

Reply to
John S

--
Thanks for that; I wasn't aware of it.
Reply to
John Fields

The default LT SPice models for standard parts don't seem to be very good, especially as regards breakdown voltages. A 1N914 has a reverse leakage of 102 nA at 100,000 volts!

John

Reply to
John Larkin

I learned about this effect years ago when I had to repair something that was oscillating because the base resistor became open on a npn circuit. I thought it was a fluke, defective transistor etc. It was later that I found out it was a known effect. Some where around 1980 or so..

And no, LtSpice wont show it. Why? I don't know.

Jamie

Reply to
Jamie

Can anybody explain the voltages and currents here?

Version 4 SHEET 1 880 680 WIRE -224 -32 -288 -32 WIRE -224 16 -224 -32 WIRE -96 64 -160 64 WIRE 64 64 -16 64 WIRE 112 64 64 64 WIRE 224 64 192 64 WIRE 64 112 64 64 WIRE 224 128 224 64 WIRE -224 160 -224 112 WIRE 64 240 64 192 WIRE 224 240 224 192 FLAG 64 240 0 FLAG 224 240 0 FLAG -224 160 0 SYMBOL diode 208 128 R0 SYMATTR InstName D1 SYMATTR Value 1N914 SYMBOL voltage 64 96 R0 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR InstName V1 SYMATTR Value -100000 SYMBOL res 208 48 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R1 SYMATTR Value 1K SYMBOL npn -160 16 M0 SYMATTR InstName Q1 SYMATTR Value 2N2222 SYMBOL res 0 48 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R2 SYMATTR Value 1K SYMBOL res -272 -48 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R3 SYMATTR Value 1K TEXT 280 80 Left 2 !.tran 0 1 0

Reply to
John Larkin

LTSpice doesn't know how to handle the reverse voltage on the base nor the reverse voltage on the anode of the diode. That is, it doesn't handle reverse breakdown as you said in your last post in this thread.

Reply to
John S

Like our QC slogan goes at work "We Test to pass not test to fail!"

Nice how there isn't any Vbe R-break down either!

Jamie

Reply to
Jamie

--
Trying to bring down a winner, as usual?

If you find fault with the diode model, why not fix it by writing your
 Click to see the full signature
Reply to
John Fields

Will Larkin even try?

No :-) ...Jim Thompson

--
| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
 Click to see the full signature
Reply to
Jim Thompson

=A0 =A0 2N2222

=A0|-

=A0 120

=3D=3D=3D

inions

s or

n

..

I believe you can just edit the standard.dio file to add a Vrev =3D xx theres several other parameters you can add to the different transistor/diode models

-Lasse

Reply to
langwadt

Any Spice is dangerous, as your recent post, with 22 volts Vbe, demonstrates. Simulation is no substitute for thinking.

Obviously it does zeners, so all the 1N914 model needs is some reverse breakdown params. It's just interesting that the model supplied doesn't have them.

The 100 kilovolts volts across a b-e junction is even more interesting. I assume that Vbr specs slow down a simulation, so weren't included.

John

Reply to
John Larkin

But look at the currents versus time!

John

Reply to
John Larkin

--
One would think that by making a statement like that you'd be
qualified as a judge of what constitutes thinking and what doesn't.
 Click to see the full signature
Reply to
John Fields

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.