A Cradle Mount for Cab04s and Procabs.


A suggestion for those that don’t want to install an “On Board” Battery Charger into their throttles after Ken L suggested on the NCE – DCC Yahoo group, that he wanted a “cradle” similar to what portable phones use.


Instead of making some “spring contacts” on some form of a cradle and suitable “pads” on the bottom of the throttle, I used the already fitted RJ12 socket as the “pads” and a RJ12 Plug as the “spring contacts”.


The throttle “cradle” was made using the “Universal Throttle Pockets” that are available from many hobby shops including Tony’s.


A suitable 9 to 12 Volt DC 1.0 Amp Wall Wart with Mark Schutzer’s On Board circuit (Select NCE Articles), “outside” or for a basic charger a “suitable” “current limiting” resistor to limit the charge current to .05 - .1 C.


On this Cradle Charger, I am using a basic resistor Charger and a relay operated by the Red Push Button to provide a Fast Charge of .5 Amp for 5 minutes. If the batteries went flat during an operating, use this fast charge for 5 minutes. This would be enough to finish the session.


You’ll have to make your own arrangements here, I’ve given you a few ideas.


Basic “resistor” charger.


AAA NiMH rechargeable batteries Amp Hour capacities range from 600 to 1200 milli Amp Hours. I use 900 mAH ones from Jaycar Electronics, my “local” hobby electronics supplier that cost $4 each. The later Eneloop AAA are $7 each here in Australia.


A trickle charge current rate of between of 45 – 90 mAs will be suitable for an “overnight” charge.


Using a 12 Volt Wall Wart, and 900 mAH batteries, the value of the current limiting resistor, would be:



A 1 Amp diode wired in series with the resistor, will stop the radio throttle’s batteries “feeding back” to the power supply if the Wall Wart is turned off.




The Wall Wart “basic” charger is connected to the “un-used” pins 1 and 6 of the throttle’s RJ12 connector. Plugging a throttle that has been modified as above, into the Cab Bus, will not do anything, as there is no power on pins 1 and 6 of the Cab Bus (as of Apr 08).






Manufacture a “plate” from .040” styrene that fits into the bottom of the “Universal Throttle Pocket” with a hole in centre for the cable. The RJ12 plug sits above the plate.


Crimp the RJ12 plug onto the cable and CUT OFF the “tang” that normally locks the plug into the socket.


Super Glue the RJ12 plug ONTO the plate, making sure that it is “square”. This provides positive contact of the wipers in the RJ12 socket.




Glue the plate onto the bottom of the Universal Throttle Pocket, making sure the plug is in the centre.


With the tang cut off, the plug WON’T lock into the throttle, allowing easy removal & installation of the throttle.


The throttle is a “sloppy” fit into the pocket, so there is a little bit of leeway, locating the RJ12 plug onto the plate.





A couple of connections still have to be made inside the throttles, connecting the “charger” to the batteries.


Shown adjacent is the Cab04. The Procab is similar.


Pins 1 and 6 of the RJ12 socket as can be seen are NOT used.


The RED wire is soldered to Pin 1 and the BLACK wire to Pin 6.





Shown is the Cab04 installation. The red and black wires from Pin 1 and 6 of the RJ12 socket are connected to the appropriate radio board connections. The Procab connections are at the “2 Pin” Black Terminal Block at the same location.


All the electronics involved with a battery charger are “outside”, with the Wall Wart.


This could be Mark’s Constant Current Charger circuit or a suitable “dropping” resistor, providing the correct current.


See Mark’s page “NCE Articles” or my pages about the .1C charge current, for these types of chargers.


Anymore than .1C charge rate, there needs to be some form of automatic “turn OFF” of the charger when the batteries are completely charged. This complicates the charger design. In most cases a .1C rate is all that is necessary.