In the “Layout&Layout Building” forum, I asked how much a simple DCC system would cost for a walk around system. One user suggested that I use "A simple DC (Not DCC) controller with a tethered throttle on a longish cord by combining a 16V AC wall wart power supply, and a home built SCR throttle (A Silicone Controlled Rectifier to turn the AC into DC, with a center-off switch for “reverse-stop-forward” and a knob for resistance/voltage adjustment) for about $50 or so."
Is this an accurate estimate on the cost, and since it is “home built” what materials might I need for a project like this. I am not concerned about 2 train operation on this layout (a 4x8, same basic design as the Soo’s Red Wing Divisoin, see photo), but since I am planning in a viewblock, tethered walk around sounds like the cheapest and simplest option.
If you are not into building your own , there are companys that make teathered DC throttles. I use a GML Rover from GML Enterprise and it works great. have had it for years. I know there are others out there but do not have names…
Since I’m not the one who wrote the suggestion, I’m not sure where the numbers came from. They actually sound a little high to me.
There are a variety of circuits for DC throttles available on the Internet and in older issues of Model Railroader. Some are explicity designed as tethered walk-around throttles; others can be turned into tethered walk-around throttles through judicious placement of control and power components.
Questions or goals you need to resolve:
Do you want the throttle to have memory? In other words, when you unplug the tether do you wnat the train to stop, or continue at the last commanded speed and direction (memory). The memory feature adds some cost and complexity, but is achieveable. On a small, single operator layout I w
In May, I bought two of these. They’re $40 each. Very fast shipping. This past weekend, I finished wiring the last of the three locations for them to plug into on my layout, and they work very nicely.
No, for what I will be doing, it won’t be neccessary.
I am not too sure about this one, what would your suggestion be?
Two, but momentum might be nice to have.
3MPH is slow enough, but my locomotives do not run too smoothly at slower speeds without pulse, so, again, I would need some help with what kind of pulse…
I use the Aristo Craft Train Engineer wireless radio throttles which have a pulse width modulation output. With all my locos it provides good steady slow speeds in the 3-4 smph range, some locos even slower.
One common charactoristic of PWM is that at whatever speed the motor starts, it is very likely to keep running steady. So if a particular loco starts at 3 smph, its very likely to run smoothly without stalling at that speed.
Full voltage pulse width modulation also works well with the typical factory lighting circuits in most locos, providing full brightness constant lighting even before the loco starts moving.
You might want to look up some of the links others and I provided you with potential throttle designs. The write-ups will give some of the advantages and disadvantages of some of the pulse waveforms and other features. Almost all the stuff about pulses comes down to trade-offs between very slow speed performance, ease of pulse generation, and potential motor overheating.
If you are not running high-end locomotives with coreless motors, overheating is generally not an issue much these days, and all but the most extreme pulses will be reasonably safe to use. N locomotives are a little more prone to overheating than HO because of their size.
Pulse suppression (or pulse injection as MRC calls it) only uses pulses for slow speed running, allowing the pulses to die out as the voltage increases. This is gentler on motors than PWM (pulse width modulation).
PWM is very easy to efficiently generate, and provides excellent low speed operation. Each pulse has a fixed 12 volt
I use the Pacematic throttle design from the December 1977 MR.
I cannot post the schematic as it is copyrighted. About 14 volts AC goes to the box, rectified and sends DC to the track. It has pulse power with a switch to disconnect pulse power. Just a few components. No memory, does have momentum and braking capability.
Bridge rectifier, three resistors, potentiometer, two transistors, couple switches. Can be modified easily to suit you.
As soon as power is supplied to the track, that power is 12 volts, being switched on and off rapidly as Fred discribed ( The Train Engineer uses a high frequency, I’m not sure eactly what the number is), so light bulbs or LED’s and their control circuits see it as full power in on - and they lght up.
I have no over heating issues using the Train Engineer with a wide range of older and newer HO locos.
Slow speed does vary a little based on the quality of motors and drives, but as mentioned before, all are at least down in the 3-4 smph range, some better.
As for ergonomics, that is my favorite thing about the Train Engineer. It has five large buttons that can be operated by touch/feel alone without looking at the unit. And it is ambidexrious for easy use in the right or left hand - a big issue for me being left handed. The buttons are: Faster, Slower, Left direction, Right direction, Emergency Stop. The buttons are large, raised and easy to identify by touch.
This is exactly what I am looking for for small yard and Misc. swiching operations at somewhat prototypical speeds. What would I need to get this (and the momentum feature too) into a handheld throttle? Would I need just a toggle switch for the momentum on-off feature?
I enjoyed the fact that you brought up ergonomics, it is what my dad does for a living and he would be happy that other people besides him care.
Although you may not be concerned about two train operation, how many engines do you plan to have on the railroad at one time? Is it only one, or are you going to have more and physically remove one and replace it with another every time you want to swap?
The only modern (uses currently available parts) throttle circuit I know of that does pulse injection is this one: http://www.awrr.com/throtl8.html
The momentum and pulse settings can be made adjustable or fixed by reading through the text. If I had any motor growl from the default values, I would try changing C3, reducing it to 1/10 of suggested value, which would push pulse frequency to 830 Hz instead of 83 Hz. With the higher frequency, you might want to half the pulse duty cycle by changing Ra and Rb. The other pulse adjustment to play with is the pulse amplitude.
Use a multi-position switch with different size capacitors to have selectable amounts of momentum, similar to how the several speed ranges are implemented on the alternate handheld.
An updated version of the Pacematic Throttle is at http://www.awrr.com/throttle_Thorne.html. The Pacematic features an adjustable pulse riding a DC component. Unlike the 1st throttle listed, the pulses don’t
That $40 PWM throttle looks nicely made, however I’d really prefer a higher frequency than 60hz. This is also an issue with many SCR throttle designs, they simply use the 60Hz AC input and let the SCR turn off naturally. But 60Hz will be an audible buzz in many locos. Problem is - a high frequency PWM above human hearing range will also have very poor performance at low throttle settings. DCC decoders that do this usually have a ‘kick start’ or ‘torque compensation’ feature to overcome th negatives of a high frquency drive. However adding this to a DC throttle would make it a bit more complciated than a $40 version. But well worth it - smooth and silent control AND the handheld won’t get hot - PWM is very efficient as far as the driver circuits are concerned because the transistor or whatever is used is operated only in 2 sattes - full on or full off, no in between like with a standard variable voltage throttle where current NOT goign to the loco because the throttle is not wide open ends up being dissipated as heat.
Just remember to clip off those RF noise suppression capacitors on Bachmann locos, they cause problems with any PWM drive, be it a DC throttle or a DCC decoder.
Our club used a variation of the below circuit. It was much simpler. We built four and I built two for myself. The 470ufd cap was ok for use and we used the throttles for almost 18 years.
The one with the 555 IC is in the below photos. I added a resistor with a switch to change the pot resistance almost in half for switching locos. More of the main pot can be used.
Two small pots are tweaked with a tuning tool to set minimum speed on the main pot. That way a slight change in the main pot and the loco starts to move.
So, you already have a control panel and/or panels where you have the block toggles mounted? And are you intending to operate the turnouts manually or with some sort of switch machine?
Looking at your original “how much” question, I didn’t see any information on how far along you were with the electrical part of the project. If you are comparing cost, you have to factor in toggle switches, panel material, and the “cost” of your time and effort to put all that together. If you already have that stuff done, then looking for the low cost option DC throttle makes sense. On the other hand, you really don’t need any blocks on a railroad of that size. And if you are going to use manual turnouts, you really don’t need any control panel. So if the goal is to get up and running quickly, then maybe you should investigate the DCC option further.
