Info req'd on keyfob R/C

[Neil Robinson]

Intrigued by this topic, especially why a 5V circuit needed a relatively high input voltage to work and with time on my hands I decided to investigate further. I ordered a dimmer from China for the princely sum of £3.77 inclusive of shipping that arrived yesterday.
Inside it looks like this.

The 5V regulated supply for the control circuit is provided by the first four components from the left.
These are a 470 Ohm resistor, a 1N4001 diode, a 10uF capacitor and a 78L05 5V regulator.

In my opinion the resistor is a good idea with supply voltages of 12V or more but is responsible for an excessive voltage drop with lower supply voltages. Without the resistor experimental results suggested that to overcome the internal voltage drops in the diode and regulator a supply of an absolute minimum of 7.2V would be required. I had a reasonably charged battery with an output of 8.8V so I used it to check. With the resistor in place the unit wouldn't work and the output of the 5V regulator was only 3.8V with a 2.8V drop across the resistor. With the resistor shorted out (and therefore an extra 2.8V available to the regulator) the regulator output was 5.05V and the unit worked well.
From this I concluded that the unit would work reliably with a nominal 8.4V battery provided the resistor was shorted out. In my opinion an effective way of doing this is to solder a wire on the underside of the board as shown below.
Naturally for supplies of 12V or more this modification isn't required.

Regarding range I suspect the state of the battery in the keyfob is relevant. I also suspect that, for the price, the battery supplied may not always be the highest spec. and freshest example of its type.

 

[ge_rik]

That's really helpful, Neil - thanks. Yes - I think the keyfob is the weakest link and so maybe I'll try taking it apart and replacing the battery.

Really useful to know the rx can be operated on less than 12v with your mod. Will be useful where space is at a premium.

Thanks again - much appreciated

Rik

 

[tramcar trev]

But then all dimmers are not the same....
This is what is inside mine....

 

[GAP]

Another idea is to contact gregh on this forum and ask him about this;
http://www.members.optusnet.com.au/satr/electronics.htm#RC
This is dead easy depending on how electrical savvy you are basic build and I think greg would gladly help with any questions, well he has with all mine so far.
I have seen this working in its basic form and it works well.
Might save a bit of hassle because all the work has been done.

 

[ge_rik]

But then all dimmers are not the same....
This is what is inside mine....

Actually, on reflection I think mine is more like this. Difficult to see as it's fixed inside my railcar but that smaller vertical board looks familiar and I know mine has four fixing holes.

Rik

 

[trammayo]

I think mine is different to either Neil's or Trev's. I'll investigate later, more pressing challenges at the monent. I agree about the Keyfob battery - this explains why, when the aerial was stretched out, it worked with a reasonable range before lunch and was absolutely carp afterwards!

 

[trammayo]

After many problems with the dimmer unit (including the aerial wire breaking off the PCB), plus a new fob battery from Maplins Ireland (dearer than the dimmer unit in the first place), I could not get it to work in a consistently good manner!

I removed it from my Railbus on Saturday and ran the vehicle manually. The dimmer unit is consigned to the pending tray (or virtually useless bin).

 

[ge_rik]

After many problems with the dimmer unit (including the aerial wire breaking off the PCB), plus a new fob battery from Maplins Ireland (dearer than the dimmer unit in the first place), I could not get it to work in a consistently good manner!

I removed it from my Railbus on Saturday and ran the vehicle manually. The dimmer unit is consigned to the pending tray (or virtually useless bin).

A shame, sounded like a good idea.

Rik

 

[tramcar trev]

Hmmmm yes I have to agree. I think these may be bi polar, one minute they work superbly next nil response...
I have upgraded to one of these which as a 3 channel RC are a bit ordinary but just to use as a 1 channel set up they seem to work far more reliably...

http://www.ebay.com.au/itm/350687616075?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

Also under consideration are a normal R/C proportional unit with a receiver and ESC (electronic speed control) and they are sensibly priced...
http://www.hobbyking.com/hobbyking/store/__16255__Hobby_King_2_4Ghz_6Ch_Tx_R
http://www.hobbyking.com/hobbyking/store/__12901__Hobby_King_2_4Ghz_Receiver
http://www.hobbyking.com/hobbyking/store/__9090__Turnigy_20A_BRUSHED_ESC.htm

Then the challenge is to control more than one tram with one controller. Looks like a receiver and ESC is going to cost around AU$14 per tram... Also available are ESC's with reverse that are used in electric cars.....

 

[ge_rik]

Hmmmm yes I have to agree. I think these may be bi polar, one minute they work superbly next nil response...
I have upgraded to one of these which as a 3 channel RC are a bit ordinary but just to use as a 1 channel set up they seem to work far more reliably...

http://www.ebay.com.au/itm/350687616075?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

Also under consideration are a normal R/C proportional unit with a receiver and ESC (electronic speed control) and they are sensibly priced...
http://www.hobbyking.com/hobbyking/store/__16255__Hobby_King_2_4Ghz_6Ch_Tx_R
http://www.hobbyking.com/hobbyking/store/__12901__Hobby_King_2_4Ghz_Receiver
http://www.hobbyking.com/hobbyking/store/__9090__Turnigy_20A_BRUSHED_ESC.htm

Then the challenge is to control more than one tram with one controller. Looks like a receiver and ESC is going to cost around AU$14 per tram... Also available are ESC's with reverse that are used in electric cars.....

I can beat that
http://www.ebay.co.uk/itm/R2-TWISTE...sGames_RadioControlled_JN&hash=item27d020ab9e < Link To http://www.ebay.co.uk/itm...mp;hash=item27d020ab9e

I've found these transmitters work with these cheapo receivers
http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=300700177078&ssPageName=ADME:L:OU:GB:3160 < Link To http://cgi.ebay.co.uk/ws/...Name=ADME:L:OU:GB:3160

See
http://www.youtube.com/watch?v=pKznXSHVTIE

I used a Mac Five controller with the test-rig above as I got a secondhand one cheap through the 16mm ngm - but I'm thinking I might use the Viper Loco controller -
http://www.mtroniks.net/details1.asp/ProductID/193/MicroViper-loco.htm < Link To http://www.mtroniks.net/d...93/MicroViper-loco.htm

it's a bit more expensive but it has cruise control which means the loco doesn't cut out if it loses the signal (or you can set the speed and turn off the transmitter).

I'm still feeling my way with battery power which is why I'm going for the cheapest options I can find.

Rik

PS - Just noticed the cost of the transmitter has risen dramatically from £2.50 to £3.50 - inflation, huh?

 

[steamskip]

Ge-rick does that ensemble you have just listed all work together? to provide a functioning rc set if so that's dead cheap and it might be capable of doing the job!

 

[ge_rik]

Ge-rick does that ensemble you have just listed all work together? to provide a functioning rc set if so that's dead cheap and it might be capable of doing the job!

Yep! If you click on the Youtube video link you can see it in action
Of course, no idea how long such a cheap transmitter will last - but it certainly does the job. I've only got as far as testing it out as per the video. I'm in the process of constructing a couple of battery powered locos so will be able to give it a better assessment once I have these up and running

So, for £5 + £5 + £26 (all inc postage) + cost of loco and batteries, you could have a 2.4gHz system up and running (or cheaper still if you use a less expensive ESC such as Trev listed).

Rik
PS I got my battery cheap as well - http://www.ebay.co.uk/itm/360657908836

 

[steamskip]

Wow that's great as soon as I get paid I will get a set !

Next question however since I am a total novice does the fact that the receiver has 3 channels mean I could have three different locos on channels 1,2&3 using three of the same transmitters? 1 for each loco just by putting the crystal in the appropriate slot and then 'latching' each transmitter to each channel?

Thanks very muchly steamskip

 

[gregh]

I can beat that
http://www.ebay.co.uk/itm/R2-TWISTE...sGames_RadioControlled_JN&hash=item27d020ab9e < Link To http://www.ebay.co.uk/itm...mp;hash=item27d020ab9e

I've found these transmitters work with these cheapo receivers
http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=300700177078&ssPageName=ADME:L:OU:GB:3160 < Link To http://cgi.ebay.co.uk/ws/...Name=ADME:L:OU:GB:3160

See
http://www.youtube.com/watch?v=pKznXSHVTIE

I used a Mac Five controller with the test-rig above as I got a secondhand one cheap through the 16mm ngm - but I'm thinking I might use the Viper Loco controller -
http://www.mtroniks.net/details1.asp/ProductID/193/MicroViper-loco.htm < Link To http://www.mtroniks.net/d...93/MicroViper-loco.htm

You've done a good job researching all this Rik. Should prompt a few more users of RC in the garden. (I'll stick with Hobbyking in Oz.)
For a reversing ESC you might look at this one:
http://www.ebay.com/itm/072-80A-Bru...rd-Reverse-parts-for-1-18-buggy-/190745097361 < Link To http://www.ebay.com/itm/0...18-buggy-/190745097361
(I haven't used it - I've tried combined speed and reversing on a mate's one, and don't like it)

 

[tramcar trev]

Wow that's great as soon as I get paid I will get a set !

Next question however since I am a total novice does the fact that the receiver has 3 channels mean I could have three different locos on channels 1,2&3 using three of the same transmitters? 1 for each loco just by putting the crystal in the appropriate slot and then 'latching' each transmitter to each channel?

Thanks very muchly steamskip

Yes, you would need a receiver for each Loco and the ESC plugged into its corresponding channel.....Then you would have to "train" yourself to work each of the 3 locos on the 2 joysticks....
You may also have to provide a separate power supply for each receiver.
Or it may prove more practical to use one 3 channel transmitter and 1 receiver for each loco, Ch1 speed/ forward/ reverse ( with the right ESC, the ones for cars have inbuilt reverse), Ch2 lights on/off, Ch3 Smoke on/off. Especially at this price, they are a steal.

 

[ge_rik]

You've done a good job researching all this Rik. Should prompt a few more users of RC in the garden. (I'll stick with Hobbyking in Oz.)
For a reversing ESC you might look at this one:
http://www.ebay.com/itm/072-80A-Bru...rd-Reverse-parts-for-1-18-buggy-/190745097361 < Link To http://www.ebay.com/itm/0...18-buggy-/190745097361
(I haven't used it - I've tried combined speed and reversing on a mate's one, and don't like it)

Thanks Greg
Still feeling my way, so any suggestions gratefully received. For remote reversing presumably the manual switch is replaced with one of your clever little servo operated DPDTs, yes?

My only concern would be that presumably this uses fail-safe rather than having cruise control - ie if the signal is lost then the loco will stop or can the fail-safe be overridden?. If not, do you find this to be a problem?

 

[ge_rik]

Next question however since I am a total novice does the fact that the receiver has 3 channels mean I could have three different locos on channels 1,2&3 using three of the same transmitters? 1 for each loco just by putting the crystal in the appropriate slot and then 'latching' each transmitter to each channel?

When I first explored this, I was of a similar mind (based on my experiences with r/c in the previous century). With 2.4gHz there's no crystals. You 'bind' the receiver to the transmitter - which usually means plugging a 'bind' plug into one of the sockets on the receiver (or on other receivers you press a tiny button) and then pressing the 'bind' button on the transmitter. On these cheapo transmitters you press and hold down one of the joysticks when you turn on the tx to bind it to the receiver. Sounds a heck of a lot more complicated than it actually is. Only takes about 5 secs to bind the rx to the tx. Only needs to be done once then the rx is bound to that tx forever (or until you decide to bind it to another tx).

No doubt Greg or Trev or someone else will correct me if I've misled you.

As Trev says, you could try running more than one loco from one transmitter but at this price you'd be better off having a dedicated transmitter for each loco. Theoretically I think you could have an infinite number of 2.4 gHz transmitters operating in the same garden as each has its own unique coding - but there probably is a finite limit (undoubtedly some large power of 2 - it's all this digital malarkey!)

Rik

 

[gregh]

Thanks Greg
Still feeling my way, so any suggestions gratefully received. For remote reversing presumably the manual switch is replaced with one of your clever little servo operated DPDTs, yes?

My only concern would be that presumably this uses fail-safe rather than having cruise control - ie if the signal is lost then the loco will stop or can the fail-safe be overridden?. If not, do you find this to be a problem?

Yes I just use a servo connected to a DPDT switch (or 3PDT to control directional lights).
I have no problem with the loss of signal problem - it never happens. I guess it is a drawback that the TX must be turned on at all times so the Tx batteries get flattened quicker. I use rechargeables in my Tx. If you let your trains run round and round all day then the Tx battery could be a problem. With the controllers I have built using Picaxe, I put in a cruise control effect so I could turn the TX off, but I never use it.

 

[tramcar trev]

Bad enough using the TV remote to change channels....

That's what Grandchildren are for - Oh and for trying to break speed records for G scale trams ....

As I have already pointed out to another staunch RC aficionado I have a vast investment in Key Fob Controllers, must be at least $6 so I'm not giving up just yet....

 

[trammayo]

Bad enough using the TV remote to change channels....

That's what Grandchildren are for - Oh and for trying to break speed records for G scale trams ....

As I have already pointed out to another staunch RC aficionado I have a vast investment in Key Fob Controllers, must be at least $6 so I'm not giving up just yet....

When you've cracked it let me know!