ph2t

[ph2t]

By Monday U.S time they *should* announce the winner.

[ph2t]

I’ve done some study and got together a schematic of the FET H-bridge.

The FETs are connected differently than the normal Transistor H-Bridge that’s stock in these cars. This is due to the fact that 4 N-channel FETs are used instead of 2 N-Chan and 2 P-Chan FETs.

Micro, could you please check this against your notes, I’d like to confirm accuracy. I’ve noticed that R14 & R15 are bypassed from the original circuit as well. You might want to put them back in because the V_GS(th) value is 1.2V for the FET you use. I read in other forums that the output is approx 3V from the RX2 chip, if you could check that it would be great. You might be saturating the FET unnecessarily.

I just got my NTMS7N03R2 fets from Onsemi.com. Gonna build it up tonight!

ph2t.

[ph2t]

It’s the blue thing with white stripes. It’s called a DIP switch. I believe each switch would turn on/off each crystal seperately.

[ph2t]

Micro, check you PM’s.:approve:

[ph2t]

OTP, the current would be limited by the R_DS values of the FET’s. On some other boards people have removed R15 & R14 from the BASE of the H-bridge transistors but I don’t think that would really increase performance. R14/R15 only need to limit enough current to fully saturate the transistors in the ciruit. For all those people who don’t know what we are talking about, this is the H-bridge of the RX pcb.

Pretty! :p

[ph2t]

Lol! Panda….. I’m too slack these days man for piano practice……As for the riff, I’m seeing some *fine* air guitar happening….
:p

[ph2t]

Dman man, now that’s a sweet ride. Well done….. You definately have tha skillz to pay tha billz…

[ph2t]

One string cost me $2 and I can get at least 5-6 antennas out of it….. I *think* I saw Micro do this to his cars first….. God I rip a lot of ideas from Micro….lol! :approve:

[ph2t]

Bilbo, the reason why the 27 and 57 might be having issues is because of RF harmonics being transmitted by the 27mhz controller. The harmonics transmit the same instructions but at a higher/lower frequency and at VERY less power. That’s why sometimes this interference you describe will happen but ONLY when the offending car is CLOSE to the controller… Is this what was happening to you? Did the 57mhz car stop playing up when you moved the 27mhz controller away?

[ph2t]

Prez, just look for LED’s that have high “mcd” values, this will give a good indication of their brightness. Normal LED’s are about 20-50mcd, brighter ones are 100+ mcd. You can get 5000mcd ones just don’t turn ’em on! lol…..

ph2t.

[ph2t]

I got mine from http://www.rs-components.com but they also stock them in your local electronics shop. Some of these shops won’t have a great range hence why I went online with my purchase.

So generally they are not hard to come by, try your local Radio Shack, they are called Tandy here in Aus.

Cheers,

ph2t.

[ph2t]

Been putting the long weekend to good use……NOT! lol….

Here’s the break lights:

Just prototypes at the moment. Once I get the brightness levels right I will SMD them onto a nice little piece of veroboard….

For really small red smd leds they pretty darn bright.

more to come……

:smiley16:

ph2t.

[ph2t]

Hmmmmm, that’s strange surfy. They are all encoded the same. Have you had any problems with the other two vids as well? They are all in DivX format.

Cheers,

ph2t.

[ph2t]

Here’s some video.

On the test bench

Night running 1

Night running 2

The LEDS aren’t as bright as I’d like them to be, but I can fix that with some more development later.

Well stage 1 done, now for stages 2 and 3!!!!!!!!!!!

ph2t.

[ph2t]

Well as promised here’s some video of the FET Mod in action.

The three cars pictured below have the following:

Silver Compact Char-G S2000, stock TOMY 2.2 motor.
Blue Compact Char-G Skyline GT-R, Perfection 3.0 motor.
Yellow MicroSizer Mistu Lancer,Perfection 3.8 motor. (FET Mod)

And see the video of how they all take off from a stop HERE.

You can now see for yourself the power of the FET Mod.

Cheers,

ph2t.

UPDATE:

Here’s the same video in MPEG format for all you turkeys without divx. 😀

Edited by – ph2t on 13 June 2003 17:40:27

[ph2t]

Well, I storta killed the LED flasher board that I had posted earlier in this thread so I went ahead and made a new one. I finally got off my but and completed the indicator lights.

Here’s a pic of the final prototype: Can you spot the LED’s?

FRONT

REAR

Here’s all the crap I managed to stick under the RX-7 case…… A fair bit goes in there.

Basically the extra pcb I put in connects to V+ & V- of the RX pcb along with the BASE side of the Left and Right steering transistors.

Video reel soon……

[ph2t]

Heya Bilbo, very creative work, well done.:approve:
Looks like we got us another techie!

What freq did the controller start off as?

Cheers,

ph2t.

Oh yeah dude, welcome to AUSMICRO!

[ph2t]

Thanks GT.

I found it HERE it’s made by International Rectifier.

I’m really interested in this mod and I’ve been dong a bit of investigating. I’ve found some other fets from On Semiconductor that have even lower R_DS values than the irlml2502.

One of them is NTMS7N03R2. It has an R_DS of 0.023. Half of the irlml2502. BUT it has a higher gate voltage meaning that the RX2 chip might not put out a high enough voltage to drive the fet.

I got some more info at home (still at #$%^& work!) which I’ll post later.

Has anyone checked out DC-DC converters? The one that comes on the RX pcb is pretty crap. It’s only rated at about 30mA, when I try to use this to power the H-bridge the whole thing dies. Some measurements I took later show that the RX pcb drains up to 170mA from the battery. This is no load, the car’s upside down on the table. At full load (motor stopped) the pcb drains up to 260mA. In idle mode standing still the car drains 5-6mA.

There’s some great possibilites here. With the right DC-DC Converter design you *should* be able to pump out 3.3V rated at 200mA+ driven off a single 1.2V battery. Now that would be a fast car, damn!

And……, oh yeah, you can order FREE SAMPLES from Onsemi.com.:shock:

More to come……

ph2t.

Edited by – ph2t on 06 June 2003 20:12:28

[ph2t]

Dudes, has anyone gotten their hands on the IRLML2502 datasheets? Been lookin’ everywhere…..

Cheers,

ph2t.

[ph2t]

I hope you’re right about those rims surfy, :approve:

ph2t.

[ph2t]

Yeah, spill dude!:smiley2:

ph2t.

[ph2t]

Removed it because the LED power board takes up the room. See my “sneek peak, next project…” thread in BCG techo.

[ph2t]

Check out the video posted in this thread earlier, purrrrdy!

[ph2t]

Not that much mate, but this is more a limitaion of the LEDs. I’m getting some brighter blue and white ones as we speak. 😉

ph2t.

[ph2t]

Let us know how you go, thanks Efarel… 😉

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