[RichG]

Hi Greg

Thanks for the extra info. Do you know how many amps the 35,000 rpm, red can motors take? Also does anyone know where I get one in the UK to do some tests with?

Have not investigated the failures any further, however have made on discovery.

Seeing that many of the bridge rectifier diodes had expired or desoldered themselves I dug out the spec for the FS1A.

I had assumed it would be a Schottky diode, however it turns out to be an ordinary silicon diode with a rating of 1 Amp, but more importantly a forward volt drop at 1 Amp of 1.3V. So this is not only losing us precious volts, but it is this power dissipation which is desoldering them.

So am now trying to source a suitable Schottky diode which should reduce the volt drop to a max of 0.5 Volts, this will also significantly reduce the power dissipation. A win

win.

Am not sure if I can find a suitable diode in the same package so solution may be to have the bridge remote from the board. This will mean that the wires from the guide go to the bridge and then to the board with it's bridge removed.

Another possibility is to resite the smoothing capacitor with the separate bridge, enabling the end centimeter of the board to be chopped off.

If it works this should be a big gain.

 

[idarroch]

Great work Rich! I hope you can find the better components we need!

Ian.

 

[NASCARUSA]

The red motors are showing about 2 amps when taking off down the long straight.We usually raced only three of these at a time due to the powerbase overload,of course the track switches are seperatly powered.We had one red motor and chip that outlasted the others by far.I will try a send you a red motor or two,as I have plenty of these too,although,unlike the chips,they are still usuable.We call em the big red chip friers.I am also getting a nice collection of junk throttle controls.Also.........if you add a second magnet to try and help hold the car on,it really cooks quick.......but it is an amazing site to see three cars run like this.

Greg

 

[RichG]

Hi Greg

Ok on the 2 Amps, no wonder the FS1A are not happy.

Will look for some 3 Amp plus diodes, these will not be the same size, so will have to be remote from the board.

If you could send me a motor that would be great, saves me having to look into and understand motors ( not my specialist subject) I assume these will just drop into something, ideally my slot.it Audi R8C or one of the Scaley Boxters?

When I have something that seems to work I will mend & mod four of the duff boards and send them back for test / destruction.

Sounds like you need some of Pete's throttles, my discard pile is growing all the time, and the ones that are ok are only just. My best throttle yesterday got a weird one when you press the LC button the car moves forward, still operating the LC's. Would not usually matter except that I use a 4 second push and hold on the LC with zero throttle to reset the display, which does not then work.

Rich

 

[RichG]

OK Guys you are going to love this.

Remember the power the lane changers separately mod,

remember the sort the throttles out mod,

well this mod is in the same league.

So a bit of a bodge but the only Schottky diodes I had in stock were wire ended SB130. Still 1 Amp but more importantly the forward volt drop at 1 Amp only 0.4 Volt.

So here they are soldered in in place of the FS1A, which remember has a 1.3 volt drop.

I have been doing my testing in a JGTC car. The modules make it very easy to change chips.

Had been running at 15 Volts. Swapped the chip and the car was uncontrollable.

Turned the volts down to get the same performance and ended up at 13.8 Volts. So only a quick test, but this is a big performance gain and has the added bonus of wasting less power.

Let's just hope the FIA don't ban Schottky diodes.

So not the ideal device. I will now try and find a better one, but has proven the point.

Scalextric please change to Schottky diodes asap, you will significantly improve performance and reduce failures.

Rich

 

[NASCARUSA]

Hello Rich,

I just mailed you a red motor,along with the #20 Toney Stewart car.The car even has the siliocn tires,as you will need them if you get the car running like I think you might.

Greg

P.S......You keep that #20 car for a test car.I think you will enjoy it.

 

[RichG]

Thanks Greg.

Look forward to receiving the car. Have just had a supplemental thought that we might be better off with two diodes in parallel on each leg of the bridge.

Trouble with diodes even schottky ones is that as the current goes up the volt drop goes up as well. Also the higher the rating of the diode in amps the higher the volt drop. So 2 in parallel could give the best of both worlds. Low volt drop at low and high current.

Just a thought.

 

[NASCARUSA]

Be warned Rich,Tony Stewart has a hard time staying on the track.Hes just a little wild and out of control.If you can get the power base to run even 4 of those 35,000 motors,you could make a million.Best Scalextric can do is there blue motors.Also,do you know anything about ICDs(implantable cardioverter defibrillator).I have one,it has a capacitor that can deliver 600 volts................any ideals?

Greg

 

[sax0607]

thanks again RichG ,
I am sourcing some diodes now ,want to put this to a test , modded chip versus standard in the same car , when done I will measure and compare lap times and top speed (new Hot Wheels radar gun)
sax

 

[drummer]

WOW, this IS getting VERY interesting!

Hats off to the man with a hat full o' chips!

 

[RichG]

Morning Guys

Just a few thoughts and snippets of information in no particular order.

The two mods can either be done separately or together.

The one with the greatest benefit is the Diode mod, as this makes the board able to drive beefier engines, improves the max volts you can get, and reduces power dissipation in the diodes.

The mosfet mod did not seem to improve performance, but should improve reliability. Remember we do not have a spec for the N02 & P03 devices so do not know how the ZXMC3A16 compares.

However bear in mind that the diode mod will put a greater load on the output mosfet and it may then fail.

However you have nothing to loose, so probably do the diode mod first, run the car, then if the mosfet fails change it.

Have not checked the plate of chips yet but visual examination only showed the N02 motor drive mosfet failing. An alternative mod may be to just change that one.

So have had a look around for alternative mosfets and diodes, this is what I have found and ordered for test.

So the first one is the device used in the early PB's and that I have put in the first modded board.
Second one is the device Slot.it is using, slightly lower spec, but cheaper.

Third one is the best dual mosfet I can find, slightly better but more expensive.

Finally I have looked for direct replacements in SOT23 packages

The PMV31XN looks a good bet for the N02 device and a nice price at 25P

Am not sure if the P03 device (motor brake) fails but the IRLML26402 is the best I can find at the moment.

Details on diodes to follow when I write it up.

Rich

 

[RichG]

So here's the best Schottky diodes I can find at the moment. Open to any other suggestions.

The FS1A is the original silicon diode with it's massive 1.3V drop, and attendant power dissipation.

Next the SB130 that I happened to have. Wire ended but much improved forward volt drop.
The SMA device is the same device size as the original, 3 Amp rating and a low forward volt drop. Probably the pick of the bunch,

but not tested yet.
The SMB device is larger, has a lower volt drop and is cheap. Not quite sure how you would fit it.

So thats it for now. Sax will be very interested to see how you get on.

Greg I have high hopes that the two mods combined will cope with the 35K motors. However I do not think the PB will take more than 3 cars at a time. However remember you should get similar performance at a volt less than you used to. So at 14V you might just squeeze 4 cars.

Have just received a Scalextric Light Blue can 30K motor, so will be able to see how the mod copes with that.

QUOTE (NASCARUSA @ 21 Jul 2006, 10:55) <{POST_SNAPBACK}>I have found the NASCARs to run well on the 30,000 rpm light blue scalextric motors...........except when using the braking buttons.The lap times increase with the dynamic brake,but the chip will fry very fast.
Greg can you expand on this, are you saying that using the Braking button fry's chips faster?

To be continiued.....

Rich

 

[RichG]

Started making a few measurements, many more to do, but these are interesting.

Standard Scalextric Boxter.

12V to the Powerbase
Max throttle at motor 10.1 Volts.
Temperature of diodes at start of test 30 deg C
Temperature of diodes max throttle wheels in the air settles at 40 deg C.
Temperature of diodes max throttle virtually stalled motor 100 deg C

Fitted 4 off the 15MQ040 Diodes

12V to the Powerbase
Max throttle at motor 11.1 Volts.

Temperature of diodes at start of test 30 deg C
Temperature of diodes max throttle wheels in the air settles at 36 deg C.
Temperature of diodes max throttle virtually stalled motor 80 deg C

So far so good.

Just as an aside if Digital ever catches on for club racing.

It's going to be really hard to scrutineer the electronics.

Rich

 

[Xlot]

Hi Richard,

which diodes are Slot.it using ?

Kudos for the measurements - I suppose when you say "Volt at max. throttle", it's with motor at no load

Ciao / Beppe

 

[RichG]

Beppe

Slot.it board uses a device marked RA 63A but can find no data on it. Would be nice to know the spec if anyone can find it.

Yes maximum throttle , car held with its wheels in the air.

Virtually stalled is wheels rubbing on the track and "virtually stalling" the motor. The temperature of the diodes rises very fast when you do this.

Not very scientific, but you have got to start somewhere.

Rich

 

[RichG]

A few more measurements, same tests as above except this time with the Scalextric Light Blue can 30K motor fitted.

Standard Scalextric Boxter with 30K motor.

12V to the Powerbase
Max throttle at motor 9.55 Volts.
Temperature of diodes at start of test 30 deg C
Temperature of diodes max throttle wheels in the air settles at 60 deg C.
Temperature of diodes max throttle virtually stalled motor 107 deg C

My temp meter at max and at that point a puff of smoke from the mosfet. However board survived.

Fitted 4 off the 30BQ030 Diodes

These are the larger SMB devices. They fill the available space but were actually easier to fit than the SMA type.

12V to the Powerbase
Max throttle at motor 10.4 Volts.
Temperature of diodes at start of test 30 deg C
Temperature of diodes max throttle wheels in the air settles at 43 deg C.
Temperature of diodes max throttle virtually stalled motor 65 deg C.

A puff of smoke from the mosfet on this board, so stoped the test, but again it survived to tell the tale. Looks like they have two lives. I suspect if I had kept the motor nearly stalled for much longer the mosfet would have blown.

On the standard board I think it would have been a close run thing between the mosfet blowing and a diode desoldering. Perhaps they were designed to be virtual fuses.

So the diodes are doing well, next thing is to start swapping mosfets.

Rich

 

[RikoRocket]

QUOTE (RichG @ 2 Aug 2006, 20:55) <{POST_SNAPBACK}>On the standard board I think it would have been a close run thing between the mosfet blowing and a diode desoldering. Perhaps they were designed to be virtual fuses.

Right, add a crash ("Most of the loose chips were the result of crashing when the cars were hot") into the equation and you can see why the diodes were coming off....

Good stuff Rich

As I had upped the motors on most of my cars this is going to be an essential mod!

 

[RichG]

No more tests yet, but a thought for the morning, and something to look out for if trawling through spec sheets looking for mosfets.

Further work needed, but my gut feeling is one of the schottky diodes is going to be fine. Going through the boards I have even the silicon diodes have very few failures, but because they get so hot they desolder. The schotty diodes are running much cooler and will probably fix that, with the added bonus of more volts for the motor.

So that leaves the mosfet. Have yet to test the ones in the chart above, but I have come across is a version called a protected mosfet. It's just like an ordinary one but has the ability to shut down. It has overvoltage, current limiting, overtemperature and short circuit protection. In other words they are bomb proof.

I think this type of mosfet combined with the Schottky diodes is the full answer.

Lower volt drop.
Ability to drive 2 Amps plus.
But then shut down, not destruction if the device is pushed too hard for too long.

You then have to return to the pits to cool down, but then everything springs back into life.

Here's a link to the data sheet on a VNS3NV04D, which is a dual N channel device if you want to see the sort of thing I am talking about. They of course come in all sizes and ratings.

http://www.st.com/stonline/products/literature/ds/7396.pdf

Problem is I can only find them in N channel not P, and cannot find any complimentary versions with P & N in one package.

Will separately have a look see if the brake circuit can be reconfigured to work with an N channel device.

Still probably the way forward as the N channel device is the key motor drive one, however if anyone comes across a suitably rated P channel protected mosfet let us know.

To be continued....

Rich

 

[astro]

Just caught up on this thread (am not a digital guy) - fantastic engineering going on!

Just had a lateral thought which might be useful in addition to Rich's great research. The boards are getting hot and expiring - and sometimes stopping the car means there is no airflow to cool the board... What about installing a fan like on PC CPU'c - powered by the rails so that it stays on even if the car stops?

No idea how much current they take or if they are available in appropriate sizes, but just a thought.

 

[injectorman]

Maybe make air intakes real and route to board....nah only joking.

Seriously does anyone have the Farnells web address where I can order?

Anyone Downunder know a good place to order such parts? Any help appreciated.
Thanks