A complete Driver Station

 

 

v  On many slot tracks I have seen, there is a very nice and very functional driver station where each driver can not only plug in his/her controller but also have some functionality that lets him/her tweak a few parameters for his/her driving (lane voltage, brakes) or have additional controls for some of the track functionality (pit entry, lights, etc)

 

v  So here is my version of a driver station, in its final embodiment. The following is hopefully sufficiently clear and self-explanatory for anyone to try to build it. Should anything be unclear (or wrong) please contact me and I'll try to help as much as I can.

 

 

v  Functionality and operation:

o    Direction switch: changes the direction of travel of a car on the track for that lane (reverses the polarity of the DC voltage to the track). Yes, this way, cars can travel in opposite directions

o    Voltmeter: provides readout of the voltage available to the track for that lane (i.e. voltage at full throttle).

o    Voltage adjustment: enables the driver to adjust in ~0.7V increments the voltage to the lane. Drivers can only adjust down from the voltage provided by the main power supply.

o    Brake switch: turns the brake wiring on or off.

o    Brakes Adjust: 15 Ohms, 15W rheostat (this is way overkill, but they are very cheap, cheaper in fact that most wire wound potentiometers).

o    Brake indicator: red when brakes are on, off when they are off.

o    Controller hookup: 3 female banana plugs along with 3 contacts (right above the banana plugs) for those controllers with alligator clips.

o    Aux 1: Temporary push button that connects whatever Signal is present on the input to the output. The green LED shows the push button is active.

o    Aux 2: Temporary push button that connects whatever Signal is present on the input (at the back connector) to the output (also at the back connector). The red LED shows the push button is active.

 

v  Obviously, the last two items in the list above (Aux 1 and Aux 2) can be tailored to any needs or can just not be used at all. As an example, the two push buttons could be used as track call buttons, as described by Brent Carlson in this article. The way the wiring is shown in the schematic diagram, the push buttons could also be replaced easily with regular switches and used for lights or any other function. Since I developed my own pit entry track piece, this is what I use the two push-buttons for, "pit entry request" (switches the pit entry lane changer on) and "pit entry cancel" (switches the pit entry lane changer off)

 

v  A word on the voltage adjustment through the diode rotary switch (details on the assembly of this part can be found here).

o    Diodes are non-linear electronic components. This means that the amount of voltage dropped (reduced) by a diode is actually a non-linear function of how much current is going through that diode. As soon as some significant current is flowing (say at least 100 mA), the voltage drop will be about 0.6-0.7 V per diode, however at very low current (no load) it will be only 0.2 to 0.3 V.

o    Thus, it is not like an adjustable voltage source where voltage can just be dialed-in and be guaranteed. In this case, to know how much the voltage setting really is, the rotary switch should be adjusted while having a car at full throttle (or close to full) on the track (I am assuming that the car will be held it with the rear wheels off the track J). Another way is to just adjust the switch while and after running a couple of laps with a car to what feels like the best setting.

o    Not all diodes are created/manufactured equal, so no two circuits built as described in this article will drop the exact same amount of voltage. When all eleven diodes are in use, variations from one circuit to another could be as much as 0.3 to 0.5 V

o    Of course, there are other ways to actually have a regulated voltage drop that is the same at all current values, but they are a bit more expensive and mostly a bit more complex to build, requiring a voltage regulator chip along with several resistors and capacitors. The goal here was to have a quick, cheap, and easy to build solution.

 

v  Here is the list of components, listed with their source, their part number, and their price. Most of these can be found at any electronics retailer and I am pretty sure that if you spend the time digging you'll find most of the stuff listed cheaper somewhere else.

 

 

v  About the components and prices above:

o    The LED panel meter used here can easily be replaced by a cheaper one: part number N01DM3A for only $8.95 http://www.elexp.com/. It can also be replaced by an LCD version: part number PM-21 for only $9.00 at www.allelectronics.com (Unfortunately for me I did not find these at the time I was looking for the components)

o    A cheaper alternative to the box used here is past number PB-4P at http://www.circuitspecialists.com/, at only $3.49. It is just a bit smaller but everything should still fit in there.

o    So the total cost of components (without the connectors and using the cheaper box and LED meter) is just under $28.00

 

v  The diodes in the table above are only rated for 1 Amp, which is plenty enough for my 1/43 set-up and probably good enough for many tracks and cars. However, more could be required for hot motors in 1/32 or 1/24 cars. Here are higher current diodes at http://www.circuitspecialists.com/:

o    3 Amps/50V                                  1N5400              $0.15 each

o    6 Amps/50V                                  6A05                  $0.21 each

 

v  As seen from the list above, the connectors are very expensive (although they probably can be found cheaper at other places than Digikey, I just have not looked for them since I got these for free originally).

o    The reason to use these or something similar is convenience. There is a header that fits right into the box (see pictures later) with pins where the wires inside the box can be soldered. Then, there is a plug (terminal block plug) that fits right in that header where each wire can be simply set in place with a simple screw (this is why it is called Terminal Block Plug in the list above). So one wire at a time can be inserted/removed easily while the whole plug can also be inserted/removed easily if and when needed.

o    If the auxiliary push buttons are not used at all, then only 6 wires are required, in and out of the box at the back: two from the track power supply, two from the 5V supply for the voltmeter, and two to the track. In this case, using banana jacks (probably red and black, same as in the list above), or running the wires straight out of the box through a hole in the back is probably best.

 

v  Also needed for this project are a Dremel tool (or equivalent to cut plastic), a power drill, wires (14 gauge and 18 gauge), heat shrink tubing (3/32 diameter) and a fine tip soldering iron (0.7 mm diameter tip, 20W is fine)

 

v  First, we need to cut all the holes in the box for the various components; that's where the Dremel and the Power Drill come into play.

o    Do not forget the hole on the side for the fuse holder (or place it somewhere else if you prefer)

o    Also do not forget holes in the back for the connectors from the power supplies and to the track.

 

 

 

v  Then, there is the schematic wiring of the driver station.

 

 

v  A picture of the inside of the box showing the wiring and the connectors in the back. If you cannot see any resistors connected to the LEDs in this picture, it is because they are hidden by the black heat shrink tubing.

 

 

v  Tips and hints:

o    Use 14-18 gauge wires for all the red/blue wires in the schematic, i.e. the wires for the track power, use 18-22 gauge wires for all the rest as these carry much less current.

o    Direction switch: do not forget the two diagonal crossed wires. When the switch is set to the right, the lane will be wired in the so-called "positive polarity", i.e. the right rail, when viewed from the top, will be at the positive voltage.

o    Brake switch and associated diode: the diode actually uses the 5V power supply to avoid any potential problems in the brake circuit and the main power.

o    Voltmeter: make sure to mount it right side up, the little dots on the display need to be at the bottom. Do not forget the 5V supply and make sure to connect the two inputs (labeled IN+ and IN-) to the proper wires inside the box.

o    Rotary switch with diodes for voltage adjustment: do not forget the little hole on top (in the box) for the blocking pin

o    Banana plugs (for alligator clips type controllers): cut the plastic housing about 5 mm on the larger side, i.e. cut to the threads. This way, these housings can be used to hold the plugs in the panel. Soldering the wires to the plugs might require some serious heat so make sure to do this while the plugs are not yet mounted in the box panel, or you might end up melting some plastic.

o    Put a drop of hot glue on the back of the LEDs after insertion in the holes of the box, this will hold them in place and also isolate the contacts.

o    Capacitor: mount it right on top of (and solder it to) the direction switch. This is the best location as it is as close as possible from the output to the track as it's role is to filter out all the RF noise potentially generated by the motors which could potentially drive the voltmeter crazy. Make sure to match the polarities of the capacitor to those of the wires on the switch.

o    Thermal fuse (self resetting fuse): In the schematics I mention 2.5 Amps while the model I quote in the list is 1.10 Amp. This is because such a fuse will sustain 1.10 Amp continuous and trip when the current surges to about 2 to 2.5 Amps.

 

v  If you want to look at another great driver station, please check out Brent Carlson's article. This one has a continuous voltage adjustment circuit and really cool looking analog voltmeters.

 

v  Another more compact driver station can be found on the Oldslotracer web site: check it out.

 

v  And here is another article by Steve Sawtelle on a simple but very nice looking driver station hookup: check it out. Steve also has other versions of his basic driver stations, well worth checking out.

 

v  Finally, here is a simplified version of this driver station, with only the direction reversing switch and the brake sensitivity adjustment.

 

v  Here is a driver station that “Showmemore” from the HRW forum, built based on this design. Great job !!!

 

 

Last Update: 8/20/06                                                                                           Drop me a note