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Discussion Starter · #1 ·
I'm installing a slot it digital chip in a NSR Porsche 917. Unlike slot it cars there is not enough space to insert the chip well forward on the chassis floor, close to the guide. But if I can extend the IR LED off the board I should be able to achieve what's needed. I have read that this can be done, but not how to do it. There is mention of soldering IR leads (I have a spare IR LED from another project) to two tabs on the chip, but which ones? The only obvious ones are a large square and circle on the back of the chip, but these just go straight to the guide wires. That doesn't seem right...

Any help appreciated.
 

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The tabs on the other side of the PCB from the 2 pads connected to the guide.

If the guide pads are on top, the IR pads are on the bottom and vice versa

gallery_11296_3058_63372.jpg
 
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Discussion Starter · #3 ·
Ah, perhaps those two tabs (on the other side) are isolated from the guide tabs, yes?
 

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yes
 
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novice jazz player &
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Just to add to the discussion... some LEDs have a resistor built in ... but most do not. My question is does this application require an LED with or without a built in resistor?

C
 

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Discussion Starter · #6 ·
Thanks for clearing this up for me, much appreciated. But I guess I should know the answer to Dr_C's Q before going ahead. (I was planning on taking the IR LED and leads off a retro fit scalextric chip that I blew).
 

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No resistor required
 

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Living the Life!
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There is an onboard resistor, it is marked 151 and just below the large chip (µ processor) in my photo above.

One thing to watch out for is that not all infra-red LEDs follow the convention for polarity. So if the lane changing does not work, try switching the leads over on the large pads. It won't hurt anything if you wire it incorrectly ......... ;) If that doesn't work then the chip itself may be duff.
 

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Discussion Starter · #9 ·
Thanks for that GregK, unfortunately my progress report is not good. I wired up as I thought correct. Digital control worked, but no lane switching. Connections all looked good. So I figured - before reading your post - that maybe the polarity of the IR LED was wrong (Scalextric give you a red and black wire, but in the land of slot cars (still fairly new to me; I'm having a break from railway modelling) wire colour doesn't seem to mean much!), which wouldn't hurt anything - it would just be non-conducting. Anyway, I wondered whether I could get the lane to switch by drifting the on board IR LED over the lane sensor by hand. This, I think, was my mistake. I now always get a power short with the (disassembled) car on the track, and meters multi-range shows an unexpected low resistance over the guide terminals; presumably I shorted the chip across the slot. So - another blown chip (was brand new), and as far as I can tell the IR LED pinched from the blown Scalextric retro chip doesn't work, and that was superglued into a (hugely overpriced) SureChange guide (these seem to be essential for front engined Fly cars, but also seemed the best solution for this NSR car with its difficult interior chassis) and won't come out! (Did I make this many mistakes when I started out in railway modelling - I don't think so, but my eye sight was better then, and my cortex!) The dollar signs just keep rolling. Time for a glass of wine...
 

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The big problem with the SP15s and the earlier SP15B (sans wings) is that the casing for the infra-red LED has a +ve voltage on the outer casing.

Try sending a PM to Marurizio (username - Slot.It) and see if something can be sorted out as this should not happen.
 
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and that was superglued into a (hugely overpriced) SureChange guide (these seem to be essential for front engined Fly cars, but also seemed the best solution for this NSR car with its difficult interior chassis)
Surechange and ARC-Pro don't play happily together.

The PB uses sensors for both the guide blade and the IR LED - the guide blade needs to pass the sensor before the IR LED to register laps on ARC-Pro
 

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Discussion Starter · #12 ·
Twigman - oh dear, that sounds like v bad/hacked engineering by Scalextric (I even checked this very point on line, and the advice was that it was okay - I think some posts are just guesses!). I'd only tested on the lane change (which works beautifully with the SureChange), not the lap count (though I'm puzzled why that should be different; perhaps only lap count requires a car ID...) - good job I decided to do this mod on only one car (Fly Panoz) and wait for a full test before committing to the others - (I have half a dozen SureChange guides in my shopping basket that I shall now remove!). So what do I do with my other front motor Fly cars (Panoz GT, Panoz LMP, Corvette, Viper)? Shifting the motor is a major hack! My track design puts at least a half straight before any lane changes - will that be enough to get away with putting the IR LED behind the front motor (a couple of inches or so behind the guide?)
 

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not the lap count (though I'm puzzled why that should be different; perhaps only lap count requires a car ID...)
the lap count is different because in analogue mode it uses the blade only - in digital registers lap with blade and IDs the car with LED

the lane changes are irrelevant to analogue mode so only use the LED

ARC-Pro requires the blade to pass before the IR LED
 

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Discussion Starter · #14 ·
Thanks Twigman - I can see this logic. But why require a blade read in digital mode? If you are reading the LED you have everything you need. So, wait. Maybe the system is not constantly on the look out - it only switches on its 'read the LED' facility when it detects a blade. But that seems a bit lame - surely it wouldn't kill the CPU to keep polling the lap counter...

Or was this just lazy engineering - the tech was half way there with analogue, so they just hacked the digital with a needless constraint?
 

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Hi folks, just to clear up one minor point, for the ARC PRO the ID signal is only detected WHILE the blade interupt sensor is also detecting the presence of the blade. Hence it is the presence of both signals AT THE SAME TIME which is required. Given the blade detect sensor is in front of the ID sensor on the track piece, the system requires the car to be configured with the blade in front of the LED. As for the question why... I am guessing (but only guessing) it is to ensure the ID signal is only detected when there is a strong signal-to-noise ratio i.e. to avoid false detections. From other posts we do however know there are other ways to ensure error-free ID detection that does not require a double sensor configuration...

Hope this helps...

C
 

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I wonder what would happen if the blade sensor were blocked so that it was always open. Would it only detect the first IR signal it saw? Would it try to detect them all? Would it have so much noise it would be useless?
 

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Great if someone could try this... but I doubt it will work (as always I may be wrong... and in this case... hopefully I am wrong!).

Having looked at the sensor circuit configuration of the ARC PRO, I plan to build a very simple little op amp based circuit which blocks signals from the ID sensor until the signal has reached a pre-determined amplitude... then the circuit will transfer a signal of the same format to the ARC PRO as it expects to see from the double sensor arrangement. However in this case the signal will come from the ID sensor only. I believe this can be done as a plug-in module as the lane sensors connect through 4 pin plugs and sockets. One track cut will also be required.

This approach should bring compatibility between ARC PRO and surechange guides... a little bit of design involved... but not much... and then some serious testing...

Anyone interested?

C
 
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I will have a go at building a simple interface circuit for connection betwen ARC PRO and its F/L sensors to achieve surechange compatibility... just ordered up some precision 5V single power supply op amps... will use LT1006s.

And, I will report back on progress...

Meanwhile, Tim999, I really like the profile photo race scene of car number 20 with the Dunlop bridge in the background... :)

C
 
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