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Comment #1 posted on 2015-09-16 10:34:42 by Jon Kulp

Thank you!

Another amazing tale of ingenuity! Well done, Bill, I loved this episode. Especially enjoyed the inadvertent detour into CAD and 3d printing. Of course the process of designing and printing 3d model is good for another episode...

Comment #2 posted on 2015-09-16 17:42:51 by Mike Ray

Hacking at it's best

Great stuff. Hacking at it's best. Heard the names of some old friends too; 2N3904, 2N2222 :-)

Comment #3 posted on 2015-09-16 21:44:19 by NYbill

Thanks, Jon.

Yea, that detour into 3D design and printing was interesting. A friend from our LUG, Jason, bought a 3D printer about 8 months ago. Asphere was interested in it and asked lots of questions. He then designed a part for one of his model rockets and asked if Jason could print it.

Before I knew it, Asphere bought his own 3D printer kit.

While designing my parts I asked Asphere, "Is this how it all starts? I'll want my own 3D printer soon." ;)

Comment #4 posted on 2015-09-16 21:48:21 by NYbill

Ha, thanks Mike.

Yep, those old 2N's...

One of those, "If it ain’t broke, don't fix it." parts.

Comment #5 posted on 2015-09-24 19:03:00 by mirwi

Splitting hair...

I agree on "old friends" for the 2N3904 and 2N2222. However, I can't resist to add that these are, unlike the 2N7000, not MOSFETS but NPN BJTs (bipolar junction transistors). With the point being that BJTs need some amount of control current at the base in contrast to the virtually zero current at the gate of a MOSFET. Judging from the linked pictures, you have compensated for that by using a bigger capacitor to get to the desired turn on time.
In any case, thanks a lot for sharing this journey.

Regards,
Michael

Comment #6 posted on 2015-09-25 09:59:46 by NYbill

Transitors

Thanks Mirwi,

I started with a MOSFET but it wasn't doing what I wanted. So, I experimented with the transistors I had on hand and chose the one that worked best for me.

However, I can't remember if I went into detail about the part change between episode 1 and 2.

Thanks for the clarification. You know, an episode on the finer points of transistors might make a fine HPR. ;)

Comment #7 posted on 2015-09-26 14:20:34 by Mike Ray

Transistors

Sadly some of the 'old friend' through-hole mounting transistors are beginning to disappear or at least be very hard to find. And those that are still there are rising in price, I guess to reflect the smaller numbers in which they are made. It's getting almost impossible to find the good old 2N3819 MOSFET I used to use to make oscillators, and even work-horses like the BC107/8/9 transistors are getting ridiculously expensive over here in the UK.

Anybody remember scraping the paint off of the body of an OCR45 to make a photo-transistor?

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