Preamble.
For a few years I have a small 45mm track in my garden. I am running G scale or IIm scale trains. It is a small single track loop with a couple additional branches. It run at ground level for some added realism. On a bed of slablayer mix. I find Wickes' slablayer great for tr a k foundation. You dig a 4" 10cm deep thrench will It with slasher and possibly add a tiny bit of cement , water It, trowel it flat it the water leaves marks and leave it. Brill and so far in the 4 years of held up well. It is a single track and not too long, about 25m. It has a main station a halt a branch station when it get to it and had a small goods yard which I will rebuild this summer and add a small branch loop.
As with any track powered train cleaning the rails for power pick up is less pleasant, even if on g scale it takes a lot less time than on my previous in door N scale. But because it is at ground level you get the occasional grass messing up the power flow.
Therefore a method less reliant on clean rails had to be found. I had seen some videos from the USA all having radio control several years ago but I was hardly available here then. But revisiting this subject YouTube has loads more information it used to have.
AS I do have DCC before I thought about stay alive DCC. I had experience with it. After some procrastination on it I decided to look into RC and on board batteries.
The first G scale train I bought myself was a Newqida 99.6001-4, one of these German type narrow gauge locs. Looks very much like the LGB one, but if you look better they may have been inspired very much by the same locomotive but there is enough difference to think it can't be a copy of the LGB one.
Anyway....
The Newqida came with rc and battery pack. Great... I thought.....
Well the loc looks very nice. But the RC is from a simple RC car. Control is a bit abrupt let's say.
Missed opportunity if you ask me. For a few £/$ more for proper RC it could have been a killer, but alas not so. Still, the loc looks good. And is quite robust.
So out with the existing RC and replace it with something else. DCC stay alive perhaps? That would not be easy as there is no power pick up of the track.
Then perhaps DCC by air. Yes.... Well that is twice as expensive as what I paid for the loc, so not quite viable from a financial perspective.
And this is the story how I went about getting Radio Control in my G scale locomotives.
Investigating Radio Control on various sites and youtube I saw Ge Rik's blog on his Peckforton layout. He had some excellent posts on RC and he used Deltang which used some other protocol. And the receiver settings can be changed to accommodate the motor fitted in the locomotive. And you could later expand with sound.
So I thought I give Deltang a go. In first relatively inexpensive Newwida loc it is just about affordable. The most suitable Deltang receiver for the G scale loc was the RX65(B) and I chose the TX22 transmitter kit which can control 12 locs. And I bought an additional transmitter to make a tx21 for programming.
This is the RX65, it's very small, like a Christmas postage stamp.
And this is The Deltang TX22 kit (images from Deltang website)
The kit came with everything you need and the instructions how to build it. If you have a bit of soldering experience it's not hard, really. I'd go for the kit unless you want to source all the components your self, can be done but when you add postage it may work out more expensive. And no I have no affiliation with Deltang or it's resellers. The Rx65 is £40-£45 and the TX22 kit about the same.
Well then what to do with the batteries?
I don't particularly like the NiCd or NiMH batteries. Last a year and then lots of chemical waste. So I diverted to what many do. It had to be Lithium. I went for the standard 18650 batteries, LG so reliable and hopefully not faked as much like the Panasonic or Samsung ones. The Lithium batteries also have much more energy per volume. A C cell NiMH has about 3Whr where as a 20% larger 18650 Li batt has 10Whr, almost 3x more energy per volume and a low internal resiatance. And the 18650 batteries have become very widespread with e-cigarrettes/vaping and e-cars becoming popular. Guess one thing to thank the tobacco industry for 😀
Lithium batteries can be dangerous and I know people who's kitchen burned down by batteries of a drone. So I need to be dead careful. So serious reading up what to do. I am lucky that I have an very sturdy electronics background. To cut a long story short, I found all work had been done for me. No baking my own pcb necessary. In fact the battery management system that is available ready made, is cheaper than 20% of the components I need to buy to make one myself. So rather then component level design, it's building with "Lego blocks".
There are tonnes of battery management system pcbs. But first I needed to know how many 18650 I could fit in the locomotive. I could cram in 4 with difficulty and 3 normally and 2 with great ease. I need about 7 to 8 volt for full speed drive so to be sure I went for 3 batteries in series getting 10-11V. with hind sight 2 would have been enough but the higher voltage make the motor starts at a slower speed as the pulse width modulated signal has a higher kick to it. So beneficial to have a higher battery voltage than you strictly need.
So add a BMS for 3 lithium batteries from eBay for a couple of pounds.
The BMS does not limit the charging current so I need some current limiting via resistors or some simple electronics. I can make a current control (CC) with a transistor a small resistor and a diodeled but I have used step down PSU before that had CC. The ready step down or buck PSU module is smaller than a transistor and heatsink and runs 87% efficient from 30V down to 2V about the battery voltage. A no brainer if you also know that the ready PSU pcb is smaller and about the same price of not cheaper and does not get as hot. So another "brick" added. Brill and so much less hassle. Source eBay or Amazon or other online shops, price about £2.00.
Advantage of the CC PSU brick is that I can run a large range of wall warts with it, anything that delivers 0.5A and 14V or higher, even AC as I added a bridge rectifier on the input. I
So I connected the step down PSU to the BMS via a diode that via switch to the RX65. The BMS in turn connects to the batteries. The RX65 has that switch on the input to prevent battery drain when not in use. The diode block current flowing back to the step down PSU when not charging. And of course I put a polyfuse/polyswitch in the power lines to the BMS, just in case, 1.5A 16V. I tested short circuiting and I works perfect, nothing gets hot, nothing blows and I get a very short 20A current spike that dies down rapidly in 2 ways, the polyfuse and the BMS current limit. If the BMS locks then I have to give it a short charge. If the polyfuse fired after 2 shorts then I only need to let it cool down.
Insert drawing.
I found the loc was running too fast. The good thing about the RX65 is that you can program the maximum speed. The programming looks a bit difficult at first but if you print and follow the instructions On the Deltang website it can be done but you do need a TX21 transmitter or reconfigure your TX22 to become a TX21. It is all on the website. Ge Rik's website has a great guide as well and a video on it. I recommend to visit his blog.
Looking at the train running with load I estimated I needed a slower speed of about 60% of what is was. When it did the programming it was after reading a few times the instructions and watching the video so I know what to expect. And it turned out it was quite easy and done in a minute or so.
This Christmas (2017) Santa for me a Bachmann 91199 locomotive.
On my Bachman 91199 Lynn but not Lynn, I could stash 2 18650 batteries in the tanks max without losing the weights and with that lose traction. This gives about 7Volt. But the motor needs about 12V for realistic max speed. No worriesI though, I simply up the voltage using a step up PSU brick. Motor needs about 0.5A so chose a 3A boost PSU brick. These bricks are rated for maximum input current, at 7V in and 13V out 0.5A out at 85% efficiency would need 1.2A input. Always overrate the components with 1.5 to 2 times to have some spare capacity and for longevity so I went for the 3A version.
The BMS was rated for 2A to 2.5A and has over everything protection.
The 2s BMS pcb is really tiny.
The circuitry is slightly different due to the addition of a step up converter PSU.
Insert diagram
I also had a cheap 2nd hand old Bachmann Porter 0 4 0, I think Bachmann 91041. This was a bit in a state. The drive gear wheel had split from using the wrong grease by the previous owner and some other minor bits wrong.
This has quite a small motor that runs at realistic maximum speeds at about 6.5 to 7.5v. I decided to go for 2 lithium 18650 battery and no step up booster.
I added a 2s BMS board and a current control step down psu for charging.
Psu from ebay, 2amp 2s BMS from Amazon.
The 0 4 0 has plenty of space inside. I put the psu and RX65 in each side tank and the BMS next the the two 18650 batteries.
The front had space for on/off push switch and charge socket.
I used melty glue as I nothing else held the type of plastic, not even superglue. I removed all the electrical contacts for the rail power. Replaced the front bulb with an LED.
Then my LGB locomotive. The motor is very robust. And needs some power. I build the same circuitry as used in the Bachmann 91199 with step up booster ps u between batteries and RX65 receiver.. But the BMS current limiting kicks in if you accelerate too fast. I had underestimated the low internal resistance of the LGB motor and maximum current it'll pull when starting to move due to inertia.
I had to replace the 2A BMS with a 3.5A version. It is only a few mm larger and fits easily. It is a thing to watch if you build a similar circuit.
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