Need DC electronics guru

[Blind Bruce]

I have a DC controller that I built from plans in the June 1977 RMC. It is called the SWAC ll and it still workes well on old locos. I would like to modify it to work on the new low current motors. I still have the schematics but don't know what to change. The new locos do not respond linearly as do the old ones. They accelerate very slowly at first until about half throttle. Then they reach top speed at a faster rate. The "pulse power" doesn't seem to have any effect also. ????
Regards,
BB

[Don Gibson]

Many of the old throttles used selenim rectifiers and rheostat's for open frame motors, your's ('77) is probably using SCR's - in any case, I doubt there is much you can modify.

Today's throttles are lower powered for today's can motors and half wave rectified DC has pretty much replaced 'pulse power', and they get more sophisticated from there. Motors with lower power consumptiom have been mated with superior gear drives, and duplicating various 'Speed Curves' is difficult at best.

Unfortunately features such as 'variable momentum' and decay have vanished in
today's price war's.

I think you will have to 'start over'. The last 'build-your-own throttles i remembet were Linn Wescot's TATIII which the parts were $100.

[nfmisso]

Hi Bruce;

As Don says, that is not a throttle for modern low current motors.

If you can scan the schematics and send them to me, I will take a look, and let you know for sure.

[Anonymous]

I built a throttle with a rheostat, a polarity switch, all mounted in a light switch box. All porbably cost me $10. That was before I went DCC so I dont use it anymore. Ill post pics when I find it[:I]

[fiatfan]

Another option is to use some of the circuits off of www.awrr.com You will find Fred very helpful if you run into problems. I have built two of his tethered walk around throttles with momentum and am very pleased with the results.

The circuits are easy to modify and experiment with. I added a second momentum capacitor (with Fred's help) and switch to allow for one acceleration rate while switching and the other acceleration rate for mainline running.

Good luck!

Tom