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Introduction
This modification adds a third sensor in the mode ABA to a single powerbase.
This will allow you to have a 3 lane start or to be able to clock laps in a pitlane alongside the start line. It will NOT allow you to identify that a car is in the pits. To do this a second power disabled powerbase is required - see thread on sector timing.
We can do all soldering on the sensing boards themselves, no need to touch the main powerbase motherboard

This rates at my difficulty rating 7/10. Wiring to the sensor track is quite difficult. The rest is easy.

What do you need?
Parts needed for this are:
One 6 car powerbase (any type including PB-Pro)
One track piece complete with sensors from either a 6 car powerbase or the new lap counter. (note 4 car powerbase does not have the necessary sensors)
Soldering iron, solder, craft knife

Preparation
The track piece with sensors has to be cut in half. This is not too difficult.
Remove the senor boards from the track.
Mark out the centreline of the track and cut with a sharp craft knife

Score both boards at the middle, and on both sides to a depth that you can feel with a thumbnail (roughly half a millimetre will do)
Bend the boards, if you have scored on both sides they should snap cleanly along the line.
We will only use the half with the wires on. Keep the other half for the future (or donate to me!)
Check wire length is OK on the half board for it to reach the terminals on the whole board. You may be lucky for a 3 lane start, almost certainly not for a pit lane. If not then you will need to replace the wires, these are sense wires with little power requirement. I generally use 4 or 6 core alarm wire, these are thin and colour coded. Try and keep the colour codes the same, or else you will get mighty confused in the future when you come back and look at it….

Board Modifications

Blade sensor Half board

Red wire stays as is. Unsolder the other 3 wires ready for connecting to different places.
White wire reconnected to the yellow pad
Yellow wire reconnected to the black pad
Black wire repositioned to the LED lower terminal


Blade sensor Whole board
Two new wires from LED to LED crossing over in an X
Cut the thin track at the very edge of the board that connects the LEDs together (marked "x" in red)
Unsolder the yellow wire from its pad.


ID sensor Half board
Remove blue wire
Reposition green wire to slim sense track (marked in red on photo). First scratch green insulator from track. Then heat track with a soldering iron and melt a tiny amount of solder onto it. Now solder wire to the track.


ID Sensor Whole board
No mods except clean and prepare the same sense track as above

Wiring up

Blade sensor Connecting

Wire half board red and black wires to the main board red and black terminals
Connect half board yellow wire to the whole board yellow wire. Do not connect to the board.
Connect half board white wire to the whole board yellow pad.


ID Sensor Connecting
Wire half board red and black wires to the whole board red and black terminals
Connect half board green wire to the whole board sense track


Assembly
I stick the half board to the track to make sure they stay in position. I use "no-nails" adhesive - you should use something similar.

Testing
Run a car across each lane. Ensure it is counting. Try a different ID car and check each lane picks up the change of ID.

Troubleshooting
Make sure all sensors work before starting this!
If no lanes count then check the cut on the blade sensor whole board
If neither the pit lane (lane 3) and lane 1 count check the yellow and white wires connections
If just lane 3 doesn't count then check the green wire is connected soundly, and check the black and red wires from half board to whole board
 

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I recently successfully built a 3 lane start using ID and blade sensing circuits that I built myself according to Tnemrap's circuit diagram below.



And here's that circuit diagram made flesh (well, silicon and plastic etc.)!



You can see where the black, red and green wires from the scratch built circuit connect to the Scalextric ID board. The circuit is just 3 resistors, a transistor and the photo sensor. I found an excellent, very small, photo sensor (T2 in the diagram) that fits under the track without fouling the car guide, the QSB363 Subminiature Plastic Silicon Infrared Phototransistor from Fairchild Semiconductor (data sheet.) It's easy to solder to the board and also seems to perform better than the Scalextric SMD ones, being more tolerant of cars with slightly higher ID LEDs (e.g when the braids are holding the car a little too high).

For the blade sensor I used the OPB610 from Optek (data sheet) It's a little tall at just over 8mm, but it seems to work perfectly. The blade sensor circuit isn't really a circuit, its only component is the OPB610! Here it is next to the Scalextric board...



You need to follow RikoRocket's guide above regarding the mods to the Scalextric blade sensor board,

QUOTE "Two new wires from LED to LED crossing over in an X, cut the thin track at the very edge of the board that connects the LEDs together, unsolder the yellow wire from its pad."
Then connect pin 1 of the OPB610 (red wire in the pic above) to the red pad, pin 2 (black) to the black pad, pin 3 (green) to the yellow wire (not the board) and pin 4 (white) to the pad you unsoldered the yellow wire from.

I had trouble working out the track to cut from RikoRocket's pic (remember the LIGHT green parts are the tracks!), so here's a clear pic of that...



...you can also see the white wire from the OPB610 soldered to what was the yellow wire's pad and the X over wires - the thinner red and black wires exiting the picture at top left.

Here it all is, wired up and glued in place (I tested the whole thing with the boards just taped in place before gluing.)
. Make sure the OPB610 slot lines up with the track slot or car guides will hit it




I used half a sensor track from an unused CLC rather than mod a single lane piece for the third lane (after all the CLC only has a sensor on one lane). That way I had the slot for the PB610 and the holes for the QSB363.

Soldering up a circuit from scratch isn't that hard. I did scour the internets to grok the basics. You really must follow the "heat the part(s), not the solder" maxim or you'll just end up with solder all over the board. You can connect the adjacent pins of components by what I call "blobbing over", basically just solder across the two board holes. Also, check the data sheets for the pin-outs of the transistor and slotted optical switch you end up using! Different transistors use different legs for C(ollector), B(ase), E(mitter) (I found this out the hard way). The pin marked with a white dot/dash on a phototransistor corresponds to the arrowed leg in the diagram. See how little I knew before I tried this?

I am now a very happy camper, mucho respect to Tnemrap and RikoRocket! If I can do this, you can too!

Here's a list of the components I used with cost in US dollars:

CODE1 x OPB610 Slotted Optical Switch $1.69
1 x QSB363 Infrared Phototransistor $0.25
1 x BC33725 Small Signal Transistor $0.16
2 x 286-2.2K-RC 2.2K Small Metal Oxide Resistor $0.49
1 x 286-4.7K-RC 4.7K Small Metal Oxide Resistor $0.49

Total $3.08

A bit cheaper than chopping up a 6 car PB, eh?
 

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An easier way (still to do it mind) is by having two PB boards side by side
This will give me three lanes and a pit lane,
This is my plan I just hope it will work, can't see why not though.
 
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