Over/under figure 8 layout. Constant speed DC HOW?

[Maletrain]

Well if you know of such a decoder...

I ran some locomotives with the meter attached to see what was going on. I'm not sure I understand it though.

Loco1 going up hill @4.6V when it gets to the top the meter reads 5V, then while going downhill @5.6V

Loco2 (high geared Heisler) 7.6V up. 8V top. 8.2V down.

So why is the voltage increasing when the loco is going down hill and presumably doesn't need as much power?

Using a Rokuhan  RC-02  http://www.zscalemonster.com/rokuhan/accessories/

Chris, I assume you are reading a volt meter across the feed wires to the track.  So, what you are seeing is the effect on the voltage that results from the change in the current drawn by the locomotive under the different load conditions.  The more current that is being drawn, the lower the voltage measurement because the greater the voltage drop through the rheostat and other wiring in your power pack.  The loco is drawing more current when it is climbing the hill, and less when it is going down, so the current is higher and thus the voltage is lower when climbing than when going down.

There are some power packs that have some compensation for that built in.  But I don't run DC, so I am not familiar with which ones those are.  The would have some internal electronics, much like what is in a decoder.

Regarding putting a locomotive decoder on the output of your power pack and using its motor leads to power your whole layout, I am not sure how that would work.  The BEMF circuitry for a decoder is probably not designed to deal with the rail-to-wheel pickup issues, so the results might be quite erratic.  Maybe somebody here who has actually tried that can post about whether real experience was successful.

I have a Model Rectifier Corp Tech 7 DC throttle that I use to test DC locos before installing DCC.  The literature for that says:

When a real locomotive is given a throttle increase there is a lag time until the preselected speed is reached. Like-wise, when braking a life-size, fast moving train it usually takes a mile or so before it stops. But because lightweight model trains won't mimic this delay on their own, we create the momentum or inertia electronically, sometimes referred to as flywheel action. Accutec Technology provides smoother performance and helps maintain the extra power when climbing grades or running over poor track conditions. Advanced slow speed circuitry allows your locomotive to crawl and couple easily.

  [I added the emphasis]

So, I suspect that throttle does what you want it to do.  But, I don't have the grades on my test layout to test that.  Maybe somebody else here can give you some first hand experience running a Tech 7 or similar DC throttle on a layout with grades?

[Point353]

I found this about it: Hand Held controller fitted with feedback electronics to maintain a constant speed when travelling up and down inclines. GMC-HH : Single Track Hand Held Controller with Feedback

Which is it you want?
Do you want to "slow the train going down hill" or do you want it to "maintain a constant speed when travelling up and down inclines"?

[pdx1955]

Really old school  would be to use a different train set (all in phase with each other)   power pack for each zone . Otherwise  a variable  resistor  for each zone could also work. Either  way would allow fine tuning for any locomotive .

[Chris333]

Otherwise  a variable  resistor  for each zone could also work.

I like this! 

Would the locomotive bridging the gaps cause any problems?

[peteski]

I like this! 

Would the locomotive bridging the gaps cause any problems?

No.The loco will simply remain running from whatever voltage is coming from the "faster" block.

But I'm also concerned about those voltage variations you are seeing. Can you measure the voltage right at the track output terminals of the throttle?  Does anybody have a schematic of that Rokuhan throttle?

If the voltage is changing that much at the output of the throttle, that means it doesn't regulate its output voltage well.  You might be better off using a simple throttle made from a LM317 3-terminal voltage regulator. It will regulate the output voltage quite well.

[Chris333]

It might be a PWM throttle. I'll try an old MRC pack later.

[peteski]

It might be a PWM throttle. I'll try an old MRC pack later.

I re-read the description and you're right. "Digital voltage control generates less heat". That means PWM. This also means that a multimeter will not accurately show the DC voltage.

While the MRC throttle is probably transistorized, it does not have good voltage regulation (not as good as the LM317).

[Chris333]

Well I do have a throttle with a LM317, but it is PWM
http://www3.sympatico.ca/kstapleton3/851.HTM

Should I use it for testing instead?

[peteski]

Well I do have a throttle with a LM317, but it is PWM
http://www3.sympatico.ca/kstapleton3/851.HTM

Should I use it for testing instead?

No, it just uses the LM317 voltage regulator to switch the voltage on and off quickly.  It is not the original intent for LM317.  If you were to eliminate about 90% of the circuitry in that throttle, you would end up with a simple DC-only regulated throttle.

The throttle would consist of the LM317, 1 resistor, one potentiometer, 2 capacitors, and a diode to protect from BEMF from the motor. That is 6 components. They you need a source of power (a transformer), bridge rectifier and a filter cap to smooth the rectiried voltage.  That is 3 more components, for the total of 9 components.  You could easily build one yourself for just few bucks.

If you have a spare throttle with accessory output, that could be substituted for the transformer.  So you have a 7-component throttle with well regulated voltage.

[Chris333]

You could easily build one yourself

Have you met me? 

If you could find a list of the components I'll start ordering. If anything it will be fun to watch the smoke when I turn it on.

[peteski]

Have you met me? 

If you could find a list of the components I'll start ordering. If anything it will be fun to watch the smoke when I turn it on.

Do you have spare throttle with accessory terminals (to use as a source of power for the throttle), or should I also include a power transformer?

I'll come up with a diagram and parts list.

[Chris333]

Do you have spare throttle with accessory terminals (to use as a source of power for the throttle), or should I also include a power transformer?

I'll come up with a diagram and parts list.

Would a wall wort work? If not include the transformer. No hurry as I'm sure shipping nowadays will screw everything up 

[Point353]

There is a schematic for the Gaugemaster throttle (and some variations on the theme) here:
https://www.scottpages.net/ReviewOfControllers.html

NTE has equivalents for the D13T1 and the C106D, and Allied has some in stock.

[Chris333]

Amazon has the Gaugemaster throttle for $33. If it would work I'd just order one.

[Chris333]

I also have a bunch of LED dimmers to make throttles from, but I believe thay are PWM as well.