S.R.M (Super Range Mod)
 

Hey everyone. Like most of you who own Microsizers I'm sick of the crappy range these things get. So I thought I'd try a few things out to improve this. First thing I tried was the telescopic antenna mod. No luck, range was still crap. I looked for the infamous "cripple capacitor", didn't find one (to be honest I didn't look too hard:D ).

Sooooo, I thought I'd do what I do best and is mod the beast!.:p
After a fair bit of research I found that you could isolate the power to the TX2 chip on the controller whilst upping the power to the RF amp to increase range. For added functionality I isolated the charging circuit as well back down to 3 volts so I wouldn't blow my nice new RX-7 Microsizer.

From the datasheet for the TX2/RX2 chipset the maximum voltage that the chip in the transmitter can handle is 5V. So I isolated this using a 78L05 (L for low power) voltage regulator to stop it from blowing up when putting 9V to it!

This is all theory at the moment. I hope to build this on the weekend so I will provide pics and posibly video to backup my findings.

For now though here is my circuit which is the original TOMY circuit modified as explained above.

Cheers,

ph2t.

http://www.prahranpianos.com/bit_g/srm.jpg

Wow! great theory. looks amazingly simple too. always expect somethin good from ph2t:D

perhaps you can add a switch also to change from single cell charge to dual cell

Thanks Modjo :).

With the 9V battery a dual batt charger is definately feasible. I'm not sure about the 1W zener diode being able to handle the current though. I'll test it first on a single cell Bit and take it from there.

Cheers,

ph2t.

ive read this 9v controller mod on a website. he made a plane out of his bit and modified his controller for range. i recall the guy said something about getting the range of 200 feet. he made a voltage regulator with a resistor, cap and diode.

Dam, that's nice work. And it would probably work :D You are really good with electronics too! Unlike me... :p

Dr1zz, you're right! :p I did get the idea from that same website. For anyone interested you can find it here .

I found that the Zener diode regulator uses more current than the 78L05 regulator. I really should add some capacitors to each side of the regulator for DC stabilisation. But since the power source is a battery and not a rectified AC supply it's not as important

As for the range of this mod, I will just have to wait and test it.;)

ph2t.

Well hurry up! I wanna see the results of this!

The 9V mod can be found in detail in the forum for indoor and micro models at www.ezonemag.com

Is this the mod you are talking about?

http://www.rcgroups.com/forums/showt...threadid=79245

ph2t.

Well, I've done the mod and didn't get the best results. Before the mod my RX7 MS got a crapy 3-4m range. Now I get about 8m, which is not bad but not what I was expecting.:(

See the pic below for the mod. I had to remove pin 9 on the TX chip from the pcb to be able to isolate the power from the rest of the board. This was a bit dodgy but it worked.

http://www.prahranpianos.com/bit_g/srm_1.jpg

Here is a (fuzzy) closeup of the mod. I haven't implemented the charger side of the circuit just the reduced 5V rail to the TX chip. I think I blew the Zener diode, during testing it wasn't dropping the voltage by 6V as it was meant to.

http://www.prahranpianos.com/bit_g/srm_2.jpg

Whilst I was at it I removed the stock antenna and replaced it with some fine enamled wire that was spiraled twice over. This added about 2 meters to the range. The wire in the pic is moving when I took the photos so it looks like two wires instead of one.:)

http://www.prahranpianos.com/bit_g/srm_3.jpg

Back to the drawing board..............:confused:

ph2t.

A great addition for anyone to start with would be losing the controller's wind up antenna and replacing it with oh, well...almost anything. ;)
The stock wind-up antenna is an absolute joke, and is probably THE biggest thing holding back the range of these fine little cars.

I was always taught that the best way to improve the performance of anything using RF is to have great antennas.

Passive improvements to get the most out of what you already have prior to, or sometimes even in lieu of "brute force" approaches that might simply throw more power into what could be (and in this case is) an inefficient radiating system.

The idea is very similar a sound system. The more efficient and resonant the speakers are, the more signal you will get per watt.

I'm thinking of replacing mine with a BNC connector and a removeable antenna.

I've had alot of success using long pieces of very thin stainless steel welding rod to make my own antennas for my ROV.

If one was to do this to a 27Mhz controller, one could use a CB antenna! (with a BNC connector cable or an adaptor)

And you didn't hear it from me, but www.ramseyelectronics.com sells a 1 watt linear amplifier kit for about forty bucks that, in theory could puch up one of these little transmitters BIG time! :cool: