Has radio control changed in the past 20 years?

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jefran
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Has radio control changed in the past 20 years?

Post by jefran » Tue May 31, 2022 8:34 pm

15 to 20 years ago I started building a pair of 16mm scale Gwalior Light Railway 2-6-2s; one steam and one battery electric. The idea was to make them very similar, so the electric loco would have full Walschaerts gear, which would be controlled by a similar reversing servo to that on the steam engine, with micro switches actually reversing the motor polarity. The speed control would be as much like the regulator as I could manage and likewise servo operated. The electric loco got as far as a basic running chassis, with the radio running nicely, but everything came to a halt for illness and has only just been revived. I found that something has seized but all that is now sorted out and I am hoping to have it running again shortly. The regulator servo only has to turn a potentiometer and I am sure that it doesn't need the full size servo that I originally fitted, so I ordered a midi sized servo, but when I plugged it in absolutely nothing happened. No movement, no noise, no heat: nothing. The reversing servo didn't work either while ever the new one was plugged in. When I reconnect the old one everything works. I had another small servo at the back of my bench, and I suspect that I had the same idea some years ago, but that didn't work when I tried it either.

The receiver is a Sanwa, and is 27MHz. The servo wiring looks about the same and the plug fits: is there some basic incompatibility that is so obvious that nobody talks about it, or have I missed something?

siclick33
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Re: Has radio control changed in the past 20 years?

Post by siclick33 » Wed Jun 01, 2022 12:10 am

What servos are you using (brand and number)?

Do you have pictures of the wiring (particularly the servo leads)? The first thing I would check, if there is absolutely no response, is that the servo is plugged in correctly; just because the plug fits doesn't necessarily mean the plug is the correct way round.

There shouldn't really be any major differences. There have been huge advances in RC over the last 15-20 years but nothing immediately springs to mind that would be causing your problems.

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LNR
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Re: Has radio control changed in the past 20 years?

Post by LNR » Wed Jun 01, 2022 3:28 am

I still run an old Sanwa transmitter in one of my boats. They were always the odd man out so far as receiver wiring is concerned. As my memory is a little hazy, I think if you plugged another brand servo into a Sanwa receiver it blew the servo, but if you plugged a Sanwa servo into another brand receiver it just didn't work but no harm was done. (memory! it could be the other way around) The pic below shows Sanwa Receiver with another brand servo plugged in and you will notice the control wire (Yellow) crossed over in the plug and I think + and - may be different too.
P6010001.JPG
P6010001.JPG (114.96 KiB) Viewed 2339 times
Grant.
PS this is 29mgs but 27mgs were the same.

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Re: Has radio control changed in the past 20 years?

Post by siclick33 » Wed Jun 01, 2022 4:03 am

The main brands (JR/Futaba/Hitec) and many others have the positive wire in the middle.

And those type of plugs can sometimes be inserted upside down which would put the signal (yellow) wire on the wrong pin.

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Re: Has radio control changed in the past 20 years?

Post by LNR » Wed Jun 01, 2022 5:03 am

siclick33 wrote: Wed Jun 01, 2022 4:03 am The main brands (JR/Futaba/Hitec) and many others have the positive wire in the middle.
Ah, it's coming back to me now. You are correct and that's why it doesn't matter because you are only mixing the control wire with the negative one.
Thanks for jogging my memory.
Grant.

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Re: Has radio control changed in the past 20 years?

Post by jefran » Wed Jun 01, 2022 11:53 am

Gentlemen,
Thank you for your help! The statement that Sanwa was the odd man out gave me an idea; I have an Acoms system on the Hunslet 2-6-4, currently stripped for rebuilding and I thought I would try the new servo in that. This system is older than the Sanwa, or at least I bought it some years earlier, and as I had at some point swapped the transmitters round, I hadn't thought there was any compatibility problem. The new servo plugged into the Acoms receiver, with the Sanwa transmitter works properly. The Kerr Stuart has all Sanwa servos, but as they are the same size as the Acoms, I will swap all the Sanwa stuff into the Hunslet and use the small servo in the Kerr Stuart with the Acoms.

The servo wiring is

Sanwa - red/black/black
Acoms - white/red/black
New one - orange/red/brown

I have a Hitec on the bench which is also red/black/black, but I have no idea when or why I bought it.

Thank you all again. I have a minor problem with the Sanwa transmitter, which may be why I swapped them over many years ago. One channel doesn't work, but the servo makes a full travel when the reverse switch is moved on the transmitter, so I am inclined to suspect wiring.

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Re: Has radio control changed in the past 20 years?

Post by big-ted » Fri Jun 03, 2022 4:52 pm

Some good info on here showing servo connection wiring of the various brands:

http://fatlion.com/sailplanes/servos.html

As mentioned, these days all brands have the positive (usually red) wire in the middle, with ground (-) and signal wires to the outside. This way, reversing the plug reverses the connection between ground and signal with no harm done other than a non-functioning servo.

In the days of old Sanwa/Airtronics used to put the positive wire to the outside. Should be pretty easy to pull the pins out of the plastic connecter with the aid of an exacto blade and swap them over.

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Re: Has radio control changed in the past 20 years?

Post by jefran » Sat Jun 04, 2022 11:12 am

Thank you - there is a lot of information there. I did a little more experimenting and the Hitec servo works with the Sanwa receiver, so I have 3 standard sized servos that do, and the very small servo I bought a long while ago works with the Acoms and is quite capable of operating the, "regulator", pot on the battery loco. So long as all this lot works, or can be coaxed back into working consistently, then I will leave these 2 locos on 27MHz and leave the servos as they are, but I now have more resources to sort out anything that stops working and more options to keep at least 1 setup in business, but for the next loco that needs radio control I think that something more up-to-date is probably the sensible way to go.

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Re: Has radio control changed in the past 20 years?

Post by Lonsdaler » Sun Jun 05, 2022 4:18 pm

Glad to hear you are on course to revive these locos. Do please just bear in mind that the 27Mhz bands are used in many of those 'cheap' R/C toys, and aren't usually tuned to a single band as used in your transmitters, so occasional erratic behaviour might be experienced. And if you're really unlucky, you may still have CB users in your area still using the 27Mhz band🤦‍♂️
Look forward to seeing your locos in action!
Phil

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My Line - https://gardenrails.org/forum/viewtopic ... 41&t=11077

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