Railbus Accessories 
Nelson Riedel, Nelson@NelsonsLocomotive.com
4/8/2017, last updated
05/27/2017
 
Ammeter: I wanted an ammeter to both show the current to the motors and also show current going back into the battery during the regenerative braking.  The typical Chinese digital ammeters measure current in only one direction.  I found this ammeter on E-Bay for less than $15 including shunt and shipping.  Arrived a few days later from Kentucky.   The seller is girogio11185.

The motors runs at less than 20 amps most the time but can go as high as 70 amps where the controller limits the current.

I measured the meter resistance (don't use lowest scale on the ohmmeter as it might peg the ammeter) to be 160 ohms.  A resistor in series with the meter leads will increase the scale.  I chose to use a 640 ohm resistor (actually used a standard value 620 ohm)  to increase the scale to ~100 amps.   I put a momentary contact switch around the resistor to revert the scale back to 20 amps  for close scrutiny of low currents.   
This is the actual circuit; pretty simple.   
Previously the motor circuit breaker had been mounted under a piece of aluminum angle.  The new larger drive cover has space for the motor circuit breaker and ammeter shunt on the back underside.     These high current components are nicely shielded here




This is the full wiring diagram  for the controller.  I don't have a bell so we can ignore that wiring. I do have front and rear head lamps, a horn and brakes so we need to discuss each of those.

Note that the diagram shows the accessories powered from 24 volts.  In some cases the controller coverts the 24 volts to 12 volts to power the accessories as described below.


Headlamps: The Critter Controller uses Pulse Width Modulation (PWM) to operate 12 volt incandescent lamps from 24 volts.  The PWM switches the negative lead from the lamps on and off about 2000 times a second.    For full brightness it is on and off exactly the same amount of time or 50% duty cycle.  The average voltage across the lamp is thus half of 24 volts or 12 volts.  To dim the lights  the duty cycle is decreased further to make the average voltage less than 12 volts.  The headlamp switch on the handset is held on for several second to turn the head lamps on and off.   A momentary push of the head light switch dims the headlamps and a second push returns them to full brightness.

In normal forward operation the headlamp switch turns on the front headlamp to full brightness and the rear lamp on but much dimmer.  The brightness of the rear lamp is set by an option in the setup menu.    When the drive is set to reverse, the rear lamp becomes the headlamp and the front lamp becomes the tail lamp.  


I originally used the front part of small LED flashlights mounted in the headlamp castings from the Goose.    I put a resistor in series with the units to operate them from 12 volts.  They weren't very bright when operated directly from 12 volts.  They worked with the Critter Controller but still weren't very bright and the dimming settings had essentially no effect. 




Next step was to  find  suitable incandescent lamps.  Lowe's stocks 12 volt  landscape spotlights in multiple power ratings.    I selected the 20 watt version in a MR-11 profile that fit within the Goose headlamp castings.

These lamps worked great, were much brighter than the old LED flashlight units and the Critter Controller dimming function worked perfectly. 

On the down side, the lamps got really hot, after 15 minutes or so the headlamp castings were too hot to hold.   The "Cooler" on the package refers to the light spectrum (warm yellow vs. cool white).  The back of the package has a warning that the lamps get very hot.

After the first run with the lamps installed --- don't know whether they were on all the time or not but at the end of the day both lamps had failed.   Don't know whether the failure was due to overheating or vibration from running on the track.  In any case, since both lamps failed they are not a viable option.     
What I wanted was a very bright 12 volt LED spotlight that was dimmable.   LEDs have very long life and consume very little power so they stay cool.   Most are not dimmable.  In fact, many are packaged with electronics that keep the light intensity constant over a wide range of voltages.  After considerable research I found the the lamps  pictured on the right from: https://www.superbrightleds.com/moreinfo/led-spot-flood/mr16-led-bulb-70-watt-equivalent-bi-pin-led-spotlight-bulb-hh/3186/6750/.  They are ~$10 each.  I tested them on 12 volts DC and they are indeed very bright!  Complete specs are on the website.  The illumination is about 600 lumens, nearly triple those 20 watt lamps described above.

I was really surprised when the Critter Controller dimming features worked perfectly. Note: I was operating the lamp from the 12 volt supply, not 24 volts.   Current drain was less than 1/2 amp at full brightness and less than 1/10 amp in the dimmed states and, the lamp don't even get warm. Unfortunately, the second lamp went out on the minimum brightness settings and the full brightness setting wasn't as bright as the first lamp tested.      
That second lamp worked fine when powered from 24 volts but got a bit warm.  That is probably OK but the 24 volts might be pushing the lamp's margins so I tried some series resistors (15, 10, 7.5 and 4.7 ohms) to find a value where both lamps worked from 24 volts and still stayed cool.   The  7.5 ohm (10 watt) resistors worked.    The challenge is to find the largest value that works.  The resistors get warm; that is heat I don't want in the lamp units.  Note that other lamps may require different value resistors.

This shows the installed front headlamp.   The lamp
is in the MR-16 profile.  I got the mounting ring from Mike Price; he uses the rings on the Critter Locomotives he manufactures.  The lamp sockets are the G4 configuration available from multiple suppliers --- I got 20 for ~ $8 at Amazon.
 



Horn:  The typical buzzer horn draws considerable current ---often 10 amps or more.  The accessory leads from the controller can handle limited current --- on the order of 1 amp.  The circuit on the right from page 22 of the manual shows how one can use a 24 volt relay to control a high current 24 volt horn.   
I already had a 12 volt horn and 12 volt relay so I hooked them up just like in the previous circuit only powered from 12 volts.   The ground from the controller that turns on the relay is not pulse width modulated like the lamp control leads; it has a 100% duty cycle.  

The drawback with this arrangement is that it runs down one battery quicker than the other --- if one blows the horn a lot. 

Brakes:   The convenience of having the brake control on the handset convinced me to purchase one of the Integral Circuits Brake Controllers.  They make two versions, the BC-100 that works with a storage reservoir (air tank) and the BC-50 that doesn't need a reservoir.  

 I chose the simpler BC-50.  The connections of the various components is  shown in the diagram on the right.   When brakes are called for on the handset the signal is sent to the Critter Controller and then on to the BC-50.  The BC-50 will then turn on the compressor.  The BC-50 monitors the pressure and when it gets to the requested pressure the power to the compressor is turned off (usually less than a second).    The line and brake cylinder will retain the air pressure and the check valve prevents it from bleeding off through the leaky compressor valves.   When the call for releasing the brakes is entered into the handset (brake button released)  the signal is sent to the Critter Controller and then on to the BC-50 where it operates the release valve to let the air out of the cylinder.

The BC-50 together with the Critter Controller monitors the air pressure and uses the combination of turning on the compressor to increase the pressure and operating the release valve to reduce the pressure.

There is a possibility that this system can oscillate so Laura suggests 1/16" ID hose be used to the release valve and the pressure sensing port.  (The normal Clippard hose is 1/8" ID.)  Also, the pressure sensing should be as close as possible to the cylinder.   I didn't have problems with oscillations but did put a restricted exhaust fitting  (~.05" ID) on the  release valve.  
This photo shows the BC-50 on the right and the Clippard ET-2-12 normally closed 12 volt valve on the left. 
This shows the Brake Controller electrical connections.   The controller housing and many of the components are used for both the BC-50 and BC-100.  As noted, there is a place to connect an Apply Valve that is not used in the BC-50 model. 

The unit is powered with 24 volts and converts the 24 volts to 12 volts for the compressor and the release valve.    
This shows the connections for pressure sensing.  Apparently the unit can also be used for vacuum brakes. 
The Compressor comes with rubber feet but no easy way to secure it.  The rubber  feet have nipples on each end.  The nipples on one end  secures the foot to the compressor.   I attached  3/32" X 1/2" base plates to the other side of each pair of feet as shown in the photo.   That is 10-32 screws that secure the base plates to the Drive Cover.    


Above is a modified wiring diagram matching the way I actually have the Railbus wired.




This shows all the electrical/electronic components except the headlamps, key switch and ammeter.  (Those components are connected by the cable on the right going up to the underside of the roof.)    All these components are attached to the drive cover which lifts out after the power leads (lower left) and motor leads (lower right) are disconnected from the terminal blocks and several cables are unplugged. 
 



The body was removed for photo above showing the left side of the Drive Cover.  That is silicone caulk covering the Fuse Block input power stud.      



This shows the back of the Drive Cover.  The aluminum plate across the bottom is attached to the frame and together with the batteries on the front side hold the cover in place.  The vertical plate on the left with the four screws  is also attached to the frame and covers the motor power wires and the speedometer pickup cable .   The controller is secured to the cover by the aluminum plate across the top edge of the cover.   The aluminum plate attached to the top of the controller provides a surface to secure the radio unit with a couple wire ties.    



This last photo shows the right side. The hose with the long brass fitting above the compressor is the feed to the brake cylinder.  The cable with large connectors on the right side is the 12 volt power for the Horn unit.   




Additional design information is at the following links:

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