Alt-BEAM Archive

Message #12546



To: beam@sgiblab.sgi.com
From: Bruce Robinson Bruce_Robinson@telus.net
Date: Sat, 25 Mar 2000 23:45:46 -0800
Subject: [alt-beam] Re: 2n2222 on H-bridge?


Dave Hrynkiw wrote:
>
> At 03:19 PM 3/25/00 , sebastiaan van Vliet wrote:
>
>> Can I just exchange the 2n3904 with 2n2222 in my H-bridge?
>> or should the 2n3906 also been replaced?
>
> Yup, otherwise you'll be getting some strange imbalances. Use
> the 2907 for the 3906.

More to the point, the main advantage of the PN2222 is much higher
current capability. There's not much point in adding that capability if
the other transistors can't handle the same current. Hence the PN2907
substituted for the 2N3906.

Hey, Dave. How come Solarbotics only sells half the '2222 / '2907 pair?
.

Bruce



12547 Sun, 26 Mar 2000 02:56:44 EST [alt-beam] Cap across the motor leads?? beam@sgiblab.sgi.com Meabadboy@aol.com In a message dated 3/26/2000 12:14:32 AM Eastern Standard Time,
sparkyg@seark.net writes:

<< remember to tell him to put a .01uf cap across his motor leads. >>

Hi,

I know partially why you do this, noise, ect. ~ but the other day I tore
apart a small toy airplane that the kids hve long sence quit playing with for
parts ~ the plane was in the shape of a f-15 and had a small gearbox with a
front and rear flashing lights ~

Anyway the motor had a Resistor sodered to each post on the motor (22 ohm) ~
but there was 3 caps sodered to the motor as follows:

1 cap was sodered between the posts of the motor had a #102 (small disk cap).
2 caps were sodered with one of the leads to the case at a common point of
the motor and one to each of the posts so that each post went to a common
point of the metal case of the motor thru a #102 disk cap

why did they do that? ~ is there a purpose to this???

Steve

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