Bipolar transistor bias question

<bloggs.fredbloggs.fred@gmail.com> wrote in message 
news:93172f92-dfda-4439-9b00-6494301eafd7@googlegroups.com...
On Tuesday, December 27, 2016 at 9:02:21 PM UTC-5, Bill Bowden wrote:
>> I think I have a working modle using just two transistors. The pulse 
>> shape
>> is not the best, but better than the original magazine circuit. .Total 
>> part
>> count is 10 verses 12 with the old circuit so I saved 2 parts. And it
>> triggers on 250mV. Haven't built it yet, I'll wait until I sell one of 
>> the
>> old ones at Doc's. I sold my original for $25 a couple weeks ago. I think
>> I've sold 6 for around $20 each, so I'm ahead $120 in a couple years.
>>

>What magazine article project are you doing?

The original article is here, but I'm doing it differently.:

http://nutsvolts.texterity.com/nutsvolts/201208/?folio=32&pg=32#pg32

<dagmargoodboat@yahoo.com> wrote in message 
news:0377f2d8-b993-4bf2-b54b-833df4c1d824@googlegroups.com...
> On Wednesday, December 28, 2016 at 7:58:39 PM UTC-5, Bill Bowden wrote:
>> <dagmargoodboat@yahoo.com> wrote in message
>> news:bf8b3efd-e741-43ff-a946-fb10cd48771d@googlegroups.com...
>> On Tuesday, December 27, 2016 at 9:02:21 PM UTC-5, Bill Bowden wrote:
>> > <dagmargoodboat@yahoo.com> wrote in message
>> >
>> > I think I have a working modle using just two transistors. The pulse 
>> > shape
>> > is not the best, but better than the original magazine circuit. .Total
>> > part
>> > count is 10 verses 12 with the old circuit so I saved 2 parts. And it
>> > triggers on 250mV. Haven't built it yet, I'll wait until I sell one of 
>> > the
>> > old ones at Doc's. I sold my original for $25 a couple weeks ago. I 
>> > think
>> > I've sold 6 for around $20 each, so I'm ahead $120 in a couple years.
>>
>> <snip LTSpice>
>>
>> That's cute.  And power consumption is down below 1mA.
>> Is your coil really 300mH?
>>
>> A nice feature is how easily you can set the output pulse width to 
>> minimize
>> power usage.
>>
>> For your amusement, here's a version of your circuit with a MOSFET 
>> output.
>> (I injected the simulated coil pick-up voltage slightly differently.)
>>
>>
>> <snip LTSpice listing>
>>
>> Interesting, and you saved another part. But it doesn't seem to work on a 
>> 2
>> volt battery. I'm figuring a couple AA cells will be close to dead at 1 
>> volt
>> each, so I need the thing to operate on 2 volts..
>
> Just tried it--works fine for me @ 1.0 V.  But you'll prefer the jellybean
> BJT's; this was just for fun.
>
>> The coil inductance may be lower at 150mH. I just looked at this air core
>> inductance calculator and plugged in the appriximate values of 150mH and 
>> 1/4
>> inch for both inner coil diameter and length.and wire gauge of #38. It 
>> shows
>> 3300 turns and about 300 ohms of resistance, which is about what I have. 
>> So,
>> the inductance may be lower at 150mH.
>
> The key thing will be whether the new coil gives the pendulum
> enough of a 'push' to keep 'er going.  Then you can tweak the
> drive pulse width to save power.
>
>> The air core calculator is here:
>>
>> http://www.pronine.ca/multind.htm
>
> Cheers,
> James Arthur

I built the circuit on a proto board and it oscillates at about 4K. If I 
pull out Q2 and plug it back in, the oscillation stops but starts again on 
the first trigger. The layout was messy so I cleaned it up with shorter 
leads but no help. Finally figured out adding another cap (.05uF) from base 
to ground of Q2 fixes the problem. It doesn't seem to matter what the cap 
value is. Works OK with 4.7nF to  0.12uF. so I settled on .05uF since I have 
a bag of those. Today, I wound a new coil with slightly larger guage and 
length. with 3000 turns and resistance of 180 ohms. I'm installing the 
circuit inside a .cigar box so all components are hidden in the box. It's 
actually not a cigar box but some sort of beauty box for women to do their 
makeup. But it's a nice looking box with inlaid wooden squares I found a 
Cypress for $2. There are 3 compartments and one of the compartments is a 
perfect fit for 2 'D' size batteries. I'm using magnets inside the box to 
hold the swinger posts in place on the top so I don't have to drill any 
holes. It's working fairly well with 7 inch posts and a 12.5 inch diameter 
swing. It's flying and starts with about a 3 inch distance from the coil. It 
didn't do too well with a tiny magnet on the pendulum. so I stacked 4 little 
magnets together and that helped a lot. I'm going to shop for a larger 
magnet to replace the 4 little ones. Efficiency is pretty good. The pulse is 
20 mS and the idle time is 400mS so the duty is about 5%. The coil draws 17 
mA so the battery drain should be a little less than 1mA. A 'D' size 
alkaline battery is 16 AH so battery life should be 16000 hours or about 667 
days. And another feature is the swinger posts and swinging magnet can all 
be removed from the top surface and stored inside the box so it just looks 
like a closed beauty box. It also convinces people about perpetual motion 
since everything on top of the box can be pulled off showing there are no 
wire connections to the box and it must be magic..  .


.  .

On Wednesday, January 4, 2017 at 7:08:40 PM UTC-5, Bill Bowden wrote:
> <dagmargoodboat@yahoo.com> wrote in message 
> news:0377f2d8-b993-4bf2-b54b-833df4c1d824@googlegroups.com...
> > On Wednesday, December 28, 2016 at 7:58:39 PM UTC-5, Bill Bowden wrote:
> >> <dagmargoodboat@yahoo.com> wrote in message
> >> news:bf8b3efd-e741-43ff-a946-fb10cd48771d@googlegroups.com...
> >> On Tuesday, December 27, 2016 at 9:02:21 PM UTC-5, Bill Bowden wrote:
> >> > <dagmargoodboat@yahoo.com> wrote in message
> >> >
> >> > I think I have a working modle using just two transistors. The pulse 
> >> > shape
> >> > is not the best, but better than the original magazine circuit. .Total
> >> > part
> >> > count is 10 verses 12 with the old circuit so I saved 2 parts. And it
> >> > triggers on 250mV. Haven't built it yet, I'll wait until I sell one of 
> >> > the
> >> > old ones at Doc's. I sold my original for $25 a couple weeks ago. I 
> >> > think
> >> > I've sold 6 for around $20 each, so I'm ahead $120 in a couple years.
> >>
> >> <snip LTSpice>
> >>
> >> That's cute.  And power consumption is down below 1mA.
> >> Is your coil really 300mH?
> >>
> >> A nice feature is how easily you can set the output pulse width to 
> >> minimize
> >> power usage.
> >>
> >> For your amusement, here's a version of your circuit with a MOSFET 
> >> output.
> >> (I injected the simulated coil pick-up voltage slightly differently.)
> >>
> >>
> >> <snip LTSpice listing>
> >>
> >> Interesting, and you saved another part. But it doesn't seem to work on a 
> >> 2
> >> volt battery. I'm figuring a couple AA cells will be close to dead at 1 
> >> volt
> >> each, so I need the thing to operate on 2 volts..
> >
> > Just tried it--works fine for me @ 1.0 V.  But you'll prefer the jellybean
> > BJT's; this was just for fun.
> >
> >> The coil inductance may be lower at 150mH. I just looked at this air core
> >> inductance calculator and plugged in the appriximate values of 150mH and 
> >> 1/4
> >> inch for both inner coil diameter and length.and wire gauge of #38. It 
> >> shows
> >> 3300 turns and about 300 ohms of resistance, which is about what I have. 
> >> So,
> >> the inductance may be lower at 150mH.
> >
> > The key thing will be whether the new coil gives the pendulum
> > enough of a 'push' to keep 'er going.  Then you can tweak the
> > drive pulse width to save power.
> >
> >> The air core calculator is here:
> >>
> >> http://www.pronine.ca/multind.htm
> >
> > Cheers,
> > James Arthur
> 
> I built the circuit on a proto board and it oscillates at about 4K. If I 
> pull out Q2 and plug it back in, the oscillation stops but starts again on 
> the first trigger. The layout was messy so I cleaned it up with shorter 
> leads but no help. Finally figured out adding another cap (.05uF) from base 
> to ground of Q2 fixes the problem. It doesn't seem to matter what the cap 
> value is. Works OK with 4.7nF to  0.12uF. so I settled on .05uF since I have 
> a bag of those.

Kinda hard to tell which or what you built, but glad you got 'er going.

> Today, I wound a new coil with slightly larger guage and 
> length. with 3000 turns and resistance of 180 ohms. I'm installing the 
> circuit inside a .cigar box so all components are hidden in the box. It's 
> actually not a cigar box but some sort of beauty box for women to do their 
> makeup. But it's a nice looking box with inlaid wooden squares I found a 
> Cypress for $2. There are 3 compartments and one of the compartments is a 
> perfect fit for 2 'D' size batteries. I'm using magnets inside the box to 
> hold the swinger posts in place on the top so I don't have to drill any 
> holes. It's working fairly well with 7 inch posts and a 12.5 inch diameter 
> swing. It's flying and starts with about a 3 inch distance from the coil. It 
> didn't do too well with a tiny magnet on the pendulum. so I stacked 4 little 
> magnets together and that helped a lot. I'm going to shop for a larger 
> magnet to replace the 4 little ones. Efficiency is pretty good. The pulse is 
> 20 mS and the idle time is 400mS so the duty is about 5%. The coil draws 17 
> mA so the battery drain should be a little less than 1mA. A 'D' size 
> alkaline battery is 16 AH so battery life should be 16000 hours or about 667 
> days.

Well over a year--that's pretty sweet.

> And another feature is the swinger posts and swinging magnet can all 
> be removed from the top surface and stored inside the box so it just looks 
> like a closed beauty box. It also convinces people about perpetual motion 
> since everything on top of the box can be pulled off showing there are no 
> wire connections to the box and it must be magic..  .

Not 'like' magic, that *is* magic.  Good for you, Bill.  I've seen your
gadgets amaze and delight scores of folks...

Cheers,
James Arthur