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Controllers and batteries?


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#1 Bazzie

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Posted 13 June 2016 - 08:20 PM

I have designed and built an interesting PWM controller, very versatile, and I've done a few things that no-one has done before. Some of these have necessitated the controller being on during lane changes etc when power is off. I have looked around for rules around controllers, and the only ones I could find were off an Aussie website and it basically just dictated two things - the controller may not increase the voltage or the available current to the track. The way I've designed it, my controller will do neither. However, some-one mentioned to me at our local club that controllers are not allowed to have batteries. Does anyone know of this rule and could you point me to where this rule is described?

 

I have two possible changes I could make if I have to, but would prefer using it the way I've designed it for now. The battery allows me to make config changes when not plugged into a track, handy feature amongst others.

 

Thanks

Eben


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#2 Ramcatlarry

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Posted 13 June 2016 - 08:29 PM

You are right on the basic "add no power to the track" concept.  MOST drag controllers will have a 9 volt battery in order to run the blast relay since most drag drack never use the red wire for grounding purposes that normal track use.  I think the basic rules of ISRA, USRA and other groups cover the NON-use of batteries and capacitors in controllers


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#3 Bazzie

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Posted 13 June 2016 - 11:05 PM

Thanks for the fast reply. I found the ISRA rulebook and I suspect there may well be many controllers out there that don't comply. Any form of capacitor, however small would break the rule. Perhaps that rule needs revising with the advent of microprocessor based controllers, all of which would need some smoothing caps to keep them stable in an otherwise very harsh electrical environment. I do like the way the Aussies moderate controllers. It's open and clear, defining the outcome rather than being too specific. I just looked up their 2016 rule - Any controller is allowed as long as it does not increase voltage to the track. If voltage increases, RPMs will increase, that's it, clear and simple.
Technically the ISRA rule is also not correct - batteries and caps store charge, not voltage so if I really wanted to I could probably contest.
Anyway, for now it is what it is, and I'm not likely to compete internationally anytime soon :)
Eben

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#4 Mark Crowley

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Posted 14 June 2016 - 08:41 AM

Wouldn't a cap provide power to the track (after a track call or end of heat) that could increase your position.  The caps in a power supply will keep the going for a second or two after you turn off the input.

Mrk



#5 Mark Crowley

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Posted 14 June 2016 - 09:05 AM

From USRA Rule book:

"Any controller/choke may be used as long as the controller/choke uses no batteries or additional power sources to increase or regulate voltage or amperage at track braid. Specifically prohibited are voltage multipliers or doublers, transformers, batteries, encapsulated components, and capacitors. Specifically allowed are simple wire chokes, and diodes. These devices lower power but do not regulate it."

 

The ISRA says:

2.3 Speed controllers:  Speed controllers are unrestricted, but they must not raise or store voltage.
 
Mrk

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#6 RaptorRacingElectronics

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Posted 14 June 2016 - 12:47 PM

In the case of microcontrollers the filtering capacitors required shouldn't be able to provide power to the track as they would be behind a voltage regulator and therfore have no direct contact with the track voltage. Although it should be noted that putting capacitors before the regulator would provide charge to the track during a no power scenario.
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#7 Mark Crowley

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Posted 14 June 2016 - 02:03 PM

I would not know if a capacitor in a controller circuit was before or after a regulator, so no capacitor rules makes sense for east of enforcement.

Mrk

 

PS:  Learning about electricity is easy.  If it shocks you the first time don't touch it a second time.


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#8 RaptorRacingElectronics

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Posted 14 June 2016 - 02:47 PM

A simple test would be to power up the controller then power it down and measure the voltage output. If theres still voltage on a controller thats off then it is illegal. No need to ban all computerized controllers outright.
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#9 Mark Crowley

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Posted 14 June 2016 - 02:54 PM

A simple test would be to power up the controller then power it down and measure the voltage output. If theres still voltage on a controller thats off then it is illegal. No need to ban all computerized controllers outright.

Good point.  Do they tech in the controllers at the big races or just the cars?

Mrk



#10 RaptorRacingElectronics

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Posted 14 June 2016 - 02:58 PM

Fair point but these controllers are purchased items if you find a controller manufacturer not meeting the specs ban it. If its a homemade controller test it. Theres no reason to outright ban new technology.
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#11 old & gray

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Posted 14 June 2016 - 04:23 PM

Good point.  Do they tech in the controllers at the big races or just the cars?

Mrk

 

The only time I have seen a controller "tech" was when the race director said "3, 2, 1, hey". The "hey" was for two cars jumping forward a foot on "1". 

This was a USRA race with external resistor controllers.


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#12 Bazzie

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Posted 14 June 2016 - 05:08 PM

Well my controller uses a LiPo but there's no way for power to go from the battery to the track, I use diodes in various places to avoid track voltage charging the battery and voltage to go back to the track from the controller. In fact, I have a 3rd safeguard - my software checks for track voltage present before it will even switch on the PWM output. That's the only way I can ensure the traction control works, also when track voltage is restored. Along with other riders, I pull my trigger flat-out before track power comes on and the car does not move. I suspect I'm ok with this then?
Worst case I would have had to go to an absolute rotary encoder - they're more expensive than the optical ones and slower to read. Would have been a pity :)

Thanks for all the useful replies guys - I need to make sure that I'm ok before our nationals in September! Not that I'm going to compete with the top guys, but still, I don't want to leave cause for contention

Eben Brand


#13 idare2bdul

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Posted 15 June 2016 - 01:14 PM

You need a real big capacitor to get much extra time. A friend had one slightly less tall than two Coke cans that could give you almost a lap, which led to the rule change. Capacitors on resistor based controllers were common in the mid to late 70's. I had a pre- turbo double micro controller that had one.


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#14 Bazzie

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Posted 15 June 2016 - 02:26 PM

With modern technology you now get 50F 2.7V caps, yes 50 Farads super capacitors that can deliver up to 4A continuous. You can get them for as little as $5 a pop. My controller could run all of its electronics excluding the output stage for 7 minutes or more off two of them, if memory serves - I did the calculations some time ago but didn't like the time needed to charge up the capacitors if the controller had turned off. They're 18mm x 40mm. Still want to get a couple though to play around with, they're really cool. There are some circuits available online where they use these caps as batteries. You get to charge/use them pretty much for the rest of your life. Their energy density is a bit low, but there are lots of applications where they make sense.

Eben Brand


#15 Mark Crowley

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Posted 15 June 2016 - 03:19 PM

Bazzie:

Keep us posted on your controller progress.  Your attempt at traction control sounds interesting.

Mrk



#16 Bazzie

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Posted 16 June 2016 - 04:21 PM

Hi Mark, I love doing embedded development, even if I just occasionally do it. If I can combine it with a hobby, even better. I've done a few interesting projects before but this has been the most interesting one yet, and most extensive. My solid state electronics goes back a while, but then Google's been a great companion! I am an electronic engineer though, working in IT.
In terms of the controller, I use an optical rotary encoder as input so it is about as linear as you can get. I get 120 steps out of full trigger travel, so control is really accurate and fine. I use 2 cheap rotary encoders on top of the hand-control for brake and sensitivity (that's version 2, still have a few hours of development / building on that, first version had one rotary controller for control and a few buttons to negotiate menus). The 2 rotaries on the handle also control all of the menu functions. You can program up to 10 cars into it. Settings are sensitivity, brake, choke (sets the top end, not the bottom end - bottom is set by sensitivity alone), choke bypass and traction control. The latter is just an adjustable limit on max acceleration. At the moment it is just a linear gradient at which power comes in, I may still experiment with expo on the acceleration, but at the moment this works well. It also has 5 curves to select from, 1 linear and the res expo. I prefer the 'bottom' curve to give finer control low down for the sharp corners. I've added a setting for the PWM frequency also, and then of course the backlight is adjustable.
I use N-channel MOSFETs with sub 2mOhm resistance for both brake and throttle - driving them was interesting though :). They can handle over 340A, so probably about the best output stage you can have on a slotcar controller. I use a polyfuse at the moment for version 2, v1 has a resettable trip switch. In version 2 I I'm about to add a software fuse to protect the polyfuse, as when they go, they can take hours to reset and often don't reset fully. We have quite a potent track power supply, so initially I blew quite a few of my lesser P-channel MOSFETs I started out with.

My biggest reason behind starting this project was money - it cost me quite a bit (and I'm on a bit of a shoe-string budget at the mo :D) to get back into the hobby, and good controllers are expensive. I did a bit of research and realised I can build one that's probably better than what's out there or at least as good as the best, and for a fraction of the cost.

Eben

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#17 Bazzie

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Posted 16 June 2016 - 04:32 PM

Oh, btw I've been using v1 the last few months and it has gone without glitch. I had a lot of teething problems with running chassis sometimes just a tad low, having fuses that wouldn't blow fast enough or at all, so blew lots of P-channels until I switched to N and then added the resettable trip. It's only a 10A one but takes well over 20A before tripping. A friend has happily run a G12 on it with no issues.

Eben Brand


#18 Mike Patterson

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Posted 16 June 2016 - 09:38 PM

Can you post some photos? The geek in me wants to see pictures! :D


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#19 Bazzie

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Posted 19 June 2016 - 02:55 PM

I tried to post some pics from my phone yesterday but Tapatalk keeps crashing, I will have to do so from my computer at some stage, had a bit of a busy weekend. V2 is mostly finished so I tested it yesterday and got 0.1s off my lap times on both LMP and S16D GTP. It has a better feel to it as my V1 handle came off an old controller and had limit switches on. In some way's it is good, but I don't believe it is as accurate.
It went without a glitch and I've gone to thicker and shorter wiring from the output stage to the track. No heat issues or anything else, and the menus and sens / brake settings while driving works great. V1 was a bit fiddly with buttons on the controller box to negotiate menus. V2 works much better with the rotary encoders.
It is still an open question whether or not 'they' are going to allow my controller at the nationals. Anyone is very welcome to test it, I will even build a test jig if needed to make it easier. Having said that, it would be very easy to build a jig that will test controllers. You need 2 tests, track power off- is there power to the track braid from the controller, and secondly voltage drop over the controller (as opposed to increase) when track power is on. A tad more difficult with PWM, may need an oscilloscope for that, but I have two, one being a smallish (old) portable. My controller will violate neither of those two tests. If only full throttle test is fine, then only a multimeter is needed.
Oh, clubs are welcome to place orders for test jigs ;)

Eben Brand


#20 Bazzie

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Posted 20 June 2016 - 04:14 PM

This is version 1

You had to push the rotary encoder on top of the handle in to toggle between setting brakes and sensitivity

 

IMG_2622 - small.JPG

 

And the second pic is V2

 

IMG_2655 - small.JPG

 

The rotary encoder is a bit bulky, but there are just so many benefits, that it certainly outweighs the looks of it for me!

 


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#21 Mike Patterson

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Posted 20 June 2016 - 08:43 PM

Eben, thanks for the photos. I won't pretend to understand how it works, but it appeals to the tinkerer in me.


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#22 Mark Crowley

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Posted 20 June 2016 - 10:19 PM

Use of the rotary encoder is interesting.  Until this thread I didn't even know they existed.  Like Mike I have no idea how you a making this thing work but I am a big fan of black boxes.  Black boxes are awesome and there is no limit to what they can do..

Mrk 



#23 Bazzie

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Posted 21 June 2016 - 03:24 AM

Yup, and in that lies the beauty, apart from getting the drive circuit and brakes right, for the most of it it's just maths and some logic. A fun project :)

Eben Brand


#24 Mark Crowley

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Posted 21 June 2016 - 08:37 AM

Yup, and in that lies the beauty, apart from getting the drive circuit and brakes right, for the most of it it's just maths and some logic. A fun project :)

Most of it math and logic????  What would make you think that we who frequent Slotblog could provide any insight on either of those mythical concepts. :crazy:  

Mrk



#25 Bazzie

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Posted 21 June 2016 - 04:10 PM

Hehe, you'll be surprised! If all else fails google's your friend!

Eben Brand






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