Modifying a GWS T4GP-2.4GHz transmitter to be compatible with an RCS EVO-B2 module.

[treetop]

Originally I was using a 27MHz Tx/Rx system in conjunction with an RCS EVO-B2.
Unfortunately I did experience intermittent radio interference which played havoc with the control system. A number of times I have had my rail car speed off on its own.
Recently I purchased a GWS system, Tx and Rx only. This is 2.4GHz, so I am hoping that I will have more success in the future.
However once I connected it all up, I soon found out that I could not select the latched output needed for my engine sound. The faster speed ramp function was also missing.
On studying the manual which came with the system I discovered that the specification stated that channels 1,2 & 4 have pulse lengths of only 1.25 to 1.75ms
and channel 3 (speed control) gives 1.1 to 1.9ms.
I then connected channel 3 (which I am not normally using) to one of the EVO-B2 inputs and it worked correctly.
Conclusion: channels 1,2 & 4 do not provide sufficient pulse width variation.
I have since been directed to a GWS document that states ?the control throws of major functions have been reduced, while throttle throws remained standard?.
Well now I know.
After some experimenting I have added a three position, spring centring toggle switch
to force channel 2 (elevator) to give maximum, short and long, pulse variations.
I do not know what the actual pulse widths are, but it works reliably.
Therefore stick 2 movement up and down gives slow speed ramping only, the toggle switch gives fast speed ramping.
The ?Trainer? button, bottom left, I have isolated, one track cut and one resistor lifted, just in case. This is wired to give maximum variation on channel 4 for my latching engine sound. This is also working well.

Photographs show front of Tx with toggle switch added next to channel 2 stick.
Inside view showing wiring from PC board ?lands? to the toggle switch and the ?trainer? button. Other photo is purely for interest, of the overall installation. EVO ?B2 on the left, my home built output board in the centre and the GWS Rx on the extreme right. (this is SO small)

 

[Tony Walsham]

Nicely done.

The next trick will be to modify the TX so that the system can be used with the RCS-BELTROL operating program to give full digital speed control.
The less than full throw of the stick problem shown here, will not be a problem for the RCS-BELTROL operating program to select direction and have 2 x sound triggers.
The other L-R stick will be modified to allow RCS-BELTROL system calibration and function programming.

 

[Del Tapparo]

I had hoped to use this transmitter for my RailBoss system, but upon testing it, I found these short comings ...

Overall, I really like the Tx and Rx packaging. Great size and price. Here are the things I don't like about it in order of least important to most important:

Tx sticks cannot be positioned to the extreme corners (e.g. full left, and full up at the same time.

The pulses on the Rx channels don't have the full range: i.e. instead of 1.0 msec to 2.0 msec from end to end, it only puts out about 1.25 msec to 1.75 msec.

The output of the Rx channels are easily overload. They can't even drive a 0.1uf capacitor, which other brands have no problem with. 0.01uf does work.

The output of the Rx channels with the TX turned off are erratic: i.e. they don't stay at a predefined level. Since my electronics count on a known value all of the time, this won't work for me.

There isn't near enough power from the Tx/Rx. With open space and line of sight communication, the range is fine. However, obstacles like rocks and mounds of dirt (common in a garden railway) cause the signal to drop out continuously, or even lose total control, where other system don't. This is what kills it for me.