Derby Talk

Our pack has the Grand Prix program and I want to build a light tree for it. Am I understanding the software help pages correctly? It looks like I can connect the lights and the starter solenoid directly to the 25 pin cable coming out of the computer? As long as everything will work off of 5 volts? I hope to get away without all the complex circuits that I've read about on this forum. Any help is appreciated.

Thanks

Sounds tempting! But, I'd be very afraid of the current capacity from the couputer's 5V line. Especially if you are sinking enough current to drive a solenoid!

In the interest of even greater participation by the youngsters, here is a functional variation that I'd like to see:

3 inputs:
Starter Ready - Resets "Racer Start", Sets "Starter Ready"
Judge(s) Ready - Resets "Racer Start", Sets "Judge(s) Ready"
Racer Start - If "Starter Ready" and "Judges(s) Ready", then Activate Starting line Tree and Gate, Reset "Starter Ready" and "Judge(s) Ready", Otherwise, ignore.

This gives one of the drivers, (e.g. the driver in Lane 1) control over the actual release of cars, but subject to the readiness of the Starter and Judges.

Drag'ngoat wrote:Our pack has the Grand Prix program and I want to build a light tree for it. Am I understanding the software help pages correctly? It looks like I can connect the lights and the starter solenoid directly to the 25 pin cable coming out of the computer? As long as everything will work off of 5 volts? I hope to get away without all the complex circuits that I've read about on this forum. Any help is appreciated.

Yes, you can control these devices with GrandPrix Race Manager on your parallel port. The limitation that you will run into is the voltage drop when using long cables. The maximum recommended cable length is 12 ft, though I have had some users achieve longer lenghts with good quality shielded cable.

A compatible light tree circuit can be found at http://grandprix-race-central.com/modul ... page&pid=9

A compatible solenoid start gate circuit is discussed at http://grandprix-race-central.com/modul ... page&pid=8.

Stan Pope wrote:Sounds tempting! But, I'd be very afraid of the current capacity from the couputer's 5V line. Especially if you are sinking enough current to drive a solenoid!

The 5V from the computer doesn't drive the solenoid, it triggers the electronic switch (MOSFET) that controls the current to the solenoid. The solenoid is powered by a separate 110V power supply (stepped down to 24V).

gpraceman wrote:

Stan Pope wrote:Sounds tempting! But, I'd be very afraid of the current capacity from the couputer's 5V line. Especially if you are sinking enough current to drive a solenoid!

The 5V from the computer doesn't drive the solenoid, it triggers the electronic switch (MOSFET) that controls the current to the solenoid. The solenoid is powered by a separate 110V power supply (stepped down to 24V).

Right! But his question was could he avoid that separate power supply and run totally off the computer's power.

I think you affirmed that would not be a good idea.

Okay, it sounds like the solenoid will need 24 volts. What about the lights? Can I run the light tree off the 5V power out of the computer? I really like the fact that the Grand Prix software has the light tree capability but I want to keep the setup as simple as possible. Although, if I'm using 110v for the solenoid anyway,,,,,,,,,,,,,,

Thanks for the feedback!

Drag'ngoat wrote:Okay, it sounds like the solenoid will need 24 volts. What about the lights? Can I run the light tree off the 5V power out of the computer? I really like the fact that the Grand Prix software has the light tree capability but I want to keep the setup as simple as possible. Although, if I'm using 110v for the solenoid anyway,,,,,,,,,,,,,,

Thanks for the feedback!

The 5V from the parallel port is not sufficient to power lights, other than LED's. You do need another power source to power regular light bulbs and the 5V from the parallel port will do the switching.

If you want simple, you can build a LED light tree. All you need for each light is a LED and a resistor hooked up to the parallel port connector. The value of the resistor is dependant on the electrical characteristics of the LED that you use. The disadvantage of LED's is that they are not as visible as regular light bulbs. The advantage is that working with low voltage DC is far safer than 110V AC. I'll see if I can dig up some low voltage DC plans.

For the start gate, I have seen some solenoids that need only 12V (car door lock solenoids for instance). With these, you can use a 12V power supply (can find them at Radio Shack) which simplifies the circuit.

Here's some plans for a 12V DC light tree and solenoid combo that will interface to the parallel port. Add a 12V power supply and you are set. These are the simplest plans that I have seen and it uses small light bulbs instead of LED's.

Schematic: http://f3.grp.yahoofs.com/v1/cAt9Q_Uy9S ... ircuit.pdf

Parts List: http://f2.grp.yahoofs.com/v1/cAt9Qym7Hl ... 20tree.pdf

You will need to join the Yahoo group that these are posted on in order to access them. http://groups.yahoo.com/group/PinewoodTimer/

Here's an example of using a car door lock solenoid:

Very very interesting!

This is a rather old thread. GPRM no longer supports triggering parallel port light trees or solenoid gates (Version 6 was the last to do so). It does support them on the serial port, however. If using both, the light tree needs to be intelligent enough to trigger the solenoid gate when the lights hit green, as the software has no way of know when that happens.