Alt-BEAM Archive

Message #10616



To: alt-beam@egroups.com
From: David Simmons devs@idirect.com
Date: Mon, 21 Feb 2000 23:48:00 -0500
Subject: [alt-beam] Re: FRED1.1 SE




Ben Hitchcock wrote:

> Hi,
>
> Good stuff! I'm glad to see others trying this circuit out.

If he can get me to buy the parts he'll build anything, and the inocents of
youth allows him to believe he can improve things.

> I'm glad that the resistor values as shown on the diagram were
> experimentally tested to be the 'best'. I am a firm believer in the TLAR
> principles of engineering (for the non-initiated, TLAR stands for "That
> looks about right") so any confirmation of my values is appreciated.

For a 9 year old it is more like HFCIGBIB (How Far Can I Go Before It Blows)
but I have to admit he tested almost every combination he could think of. Of
couse it is much simpler when you use a dial resistor disc. A great little
tool that he paid a buck for, 9 cents for the blown resistors, and twenty
minutes to desolder and resolder.

> > Can anyone explain way this seems to work so well?
>
> At a rough guess, I'd say that the cap is storing up energy between pulses
> ofthe motor. Pulses? I hear you say?
> Well, most DC motors have brushes that contact a rotating armature. When
> the armature is spun, the brushes 'commutate' the current so that the
> force exerted by the magnetic field created by the armature is always in
> the one direction.
>
> In english, the brushes 'turn on' when the rotating bit is in the right
> place, which results in current spikes.
>
> I would try getting rid of the LED altogether, and only having a cap
> across the motor. This will enhance the effect (if it is what I think it
> is).
>

We dropped the LED, it made a very slight difference, but he is going to put
it back. Sometime before the weekend he is going to made a SYMET out of his
last motor with half a FRED, and then on the weekend we go get a few more
motors and he is going to try his hand at his first FRED photovore. He likes
the idea of the LED glowing very bright just before the motor fires, but for
the Photovore he will leave them out. I can't wait to see him try to freeform
this one, I'll have to make sure he has loads of spare parts on hand.

> Good luck!

Thanks, I'll need it!

>
>
> Ben
>

Regards,
Dave



Home