Power Pack with Impulse?

[GerFust]

I need better slow speed control of my old locos. I remember reading about using something think was referred to as impulse. That is, an intermittent rather than constant DC current. My layout is small, so only need to control 3-4 locos at a time at most. Do any commercially available power packs have that feature? Obviously, for a small layout I want to go as cheap as I can and get this feature in a power pack.

MRC's "Accutec technology" might, but I'm not sure from the website description.

If not, is this recommended? Anyone have plans on how to build this circuit so I can wire onto the terminals of my current DC power packs?

Thanks,
Jer

[Anonymous]

I don't know if you can add it, but the Tech 2 series from MRC has "pluse" on most models. I got mine in excellent condiditon in the "used" section of my local train shop. Cost less than 1/3 full retail.

Andrew

[GerFust]

Andrew:

That is perfect. I'm bummed, though. It never occured to me to look for one used. I was just at a train show and should have asked about this last week! :-(

Thanks,
-Jer

[Anonymous]

I guess I should add:

I believe "pulse" is AC added to your DC. Used, as you noted, to help slow speed operations go more smoothly. It usually "fades" away as you apply more power.

Using it constantly can cause the motor to build up more heat than normal. I have used it with both an old IHC/Mehano 4-6-2, and my new P2K 0-6-0 with no noticable effects.

I belive that the newer Tech 4 packs have pulse "automatically" activated - this is in part their "Accutec technology", but you're right - it is hard to tell from the website description...

Good luck.

Andrew

[ndbprr]

Not quite right yet! DC is created by a diode bridge in a power pack so when the current flow reverses in AC the diode bridge switches the flow to DC and keeps it going in the same direction. Pulse power eliminates half of the output of the diode bridge. If you remember the old sin wave from Physics class pulse power just give you 1/2 of it so it "pulses". You can create pulse in any power pack by inserting a switch in one side of the diode bridge and turning it off when you want pulse and on when you don't. Most engines do start and run slower with it but once they are moving it is better to switch to regular power as it casues some heat build up in the motors at higher voltages.

[Anonymous]

Thanks for the explanation ndbprr... I guess I was "half" right... so to speak. Sorry, that's a terrible pun... [:)]

Andrew

[Anonymous]

Tech 4 MRC 260 makes one called the tech4 350, of course, this makes the train go 1/4 and inch a minute. Perhaps "too" slow........

[Anonymous]

MRC is the way to go for pulse packs. Todays pulse packs are not simply 1/2 wave devices, but rather generate a 12-16 volt pulse of various widths. The widths of the pulse control the speed and the high voltage helps the motor cog and overcomes track and wheel resistance better than trying to run at 2 volts DC. MRC packs don't cost that much new retail. FRED

[GerFust]

Okay, I found some Tech II on eBay. Once of them states "THIS IS NOT A POWER PACK, it requires a model train controller for operation."

I'm missing something. Does this not have all you need to connect to the track and go?

-Jer

[nfmisso]

Jer;

Looke for a MRC Tech II model 1500 or model 2500. The only real difference in current (number of locos) output capability. These will run your locos as well as anything can.

There are (were) many packs and accessories in the Tech II line, stick with the 1500 or 2500.

[GerFust]

Nigel:

Thanks, that is great advice. Despite the many, many listed on eBay, the list is narrowing quickly.

-Jer

[Anonymous]

I use MRC Tech II Railmaster 2400's in a dual cab DC enviroment. I switch pulse "on" only when connecting rolling stock. It is "off" most of the time and have never experienced heat build up.

[ndbprr]

You won't if using it for switching. It is at higher voltages that you get the heat buildup. Basically with pulse you are forcing the motor to cog by interupting the power 60 times per second. It is at high motor speeds where it is alternately a user and generator of power that it happens.