Has anyone done any of these track ideas?

Other race electronics and general electronics discussions.
Post Reply
scyank
Apprentice
Apprentice
Posts: 6
Joined: Sun Jan 28, 2007 4:40 pm
Location: South Carolina

Has anyone done any of these track ideas?

Post by scyank »

Laser finish line (one per lane)
Magnetic remote starter with timer switch built in
Tongue & groove wood/plastic for the track (cheap laminate flooring?)
Acrylic track (I know, expensive but could be cool looking)
SuperDave

Re: Has anyone done any of these track ideas?

Post by SuperDave »

Laser finish line (one per lane)

[Moderator cut - no negative advertising]
Magnetic remote starter with timer switch built in

This seems to be two ideas stuck together that I prefer to separate, namely remote starter and timer.

Remote starters usually use a solenoid (a big electromagnet that pulls in a metal rod) to release a gate. Mechanically, it's fairly simple. Electrically is another matter. To release the gate, apply power. BUT, when you release the power, the stored electrical energy in the electromagnet 'flys back' (think of the spark ignition coil on your car). That flyback voltage can reach thousands of volts and typically reset every nearby computer if not blow up sensitive electronics. I got a call once from someone using our early DOS timers that spent all night twisting wire, adding aluminum foil shielding!, separating wires, etc. because they were trying to add a solenoid start to our system that at that time did not have one. There are solutions but they're more technical than space here allows.

Now, on to the 'timer switch built in'. Generally, the timer should start based on the gate drop, not on the solenoid being energized. Since the solenoid could be more sticky one time than another, for example with more cars on the gate, timing based on gate drop is more reliable.

Both ideas are highly recommended as ways to enhance the experience for the kids. Both ideas are available in commercial products. And, there are ideas on the web, but caveat builder.
Tongue & groove wood/plastic for the track (cheap laminate flooring?)

You cannot imagine a track material (or shape or length) that has not been used at one time or another in the over 50 year history of the Pinewood Derby. While our SuperTrack is made from (tongue and groove actually) ABS Plastic, other commercial tracks can be found that are made from different kinds of plywood, aluminum, even steel framed kitchen counter top. And, I know of several home made acrylic tracks.

[/quote]
scyank
Apprentice
Apprentice
Posts: 6
Joined: Sun Jan 28, 2007 4:40 pm
Location: South Carolina

Re: Has anyone done any of these track ideas?

Post by scyank »

I know about the solenoid releases and the issues that are tied to them.

I was thinking of using an energized electro magnet to hold the gate closed on one side of the gate and a microswitch on the other (to minimize magnetic/electrical interference). When you hit the button to cut the energy to the magnet, the gate would swing open and the microswitch would trigger the timing to start.

What about the use of LEDs for the finish line?
User avatar
gpraceman
Site Admin
Site Admin
Posts: 4926
Joined: Fri Jun 20, 2003 12:46 am
Location: Highlands Ranch, CO
Contact:

Re: Has anyone done any of these track ideas?

Post by gpraceman »

There are advantages/disadvantages to each means of determining when a car finishes. With lasers, you will run into alignment issues because of the tight beam. They do also draw a lot of power and could overheat over the course of a long race. I've seen overheat and alignment issues when trying to use a laser sensor arrangement at the start gate.

IR photo sensors are the most popular means of detecting a finish, with commercial timer manufacturers and Do-It-Yourselfers. There can be issues with sun light, flash photography and ambient lighting. However, there have been several discussions on Derby Talk relating to some simple things you can do prevent flash and ambient light from being a problem. Sunlight can be more of a problem, if you choose to have races outside or in a very sun lit room. Then you will need to get sensors and emitters that will work in sunlight or provide a lot of shading. New Directions uses such sensors on their timers with the "Sunlight Max" option.

I have seen a plexiglas track. It is rather cool, but I'm sure that as time goes on and its gets scratched up, it won't look as good. You can check it out at http://awanagrandprix.com/track/default.asp

I would caution you about getting too exotic. Build for reliability and longevity. Simplicity is often better than complexity. If you do build some type of solenoid or magnetic gate release, make sure you have a manual means to release, in case there are ever problems with the electronics.
Randy Lisano
Romans 5:8

Awana Grand Prix and Pinewood Derby racing - Where a child, an adult and a small block of wood combine for a lot of fun and memories.
SuperDave

Re: Has anyone done any of these track ideas?

Post by SuperDave »

I was thinking of using an energized electro magnet
When you work the physics including both the weight of the gate and the weight of the cars as well as the moment arm of those weights it is usually the case that the force required to hold it all up is significant. In that case it probably is a better idea to energize to release rather than de-energize to release. The duty cycle is then <<1% as opposed to >>99% which allows for a much more powerful device in a much smaller package. Note, that any de-energize still creates the troublesome flyback pulse and the need to clamp it appropriately.
What about the use of LEDs for the finish line?
[Moderator cut - no negative advertising]
User avatar
Dethrider
Apprentice
Apprentice
Posts: 12
Joined: Sun Feb 18, 2007 8:38 pm
Location: Stewartsville, NJ

Re: Has anyone done any of these track ideas?

Post by Dethrider »

To reduce or eliminate the transiesent from the solenoid coil, apply a ceramic capacitor across the coil. When power is removed, the capacitor will absorb the transiesent spike.

Aluminum foil will not work.
NealOnWheels
Apprentice
Apprentice
Posts: 23
Joined: Thu Mar 30, 2006 11:38 am
Location: Rolling Prairie, Indiana

Re: Has anyone done any of these track ideas?

Post by NealOnWheels »

To eliminate solenoid coil transients I would recomend using a appropriately sized diode or other transient voltage suppressor instead of a capacitor.

A capacitor may reduce somewhat the EMI that can reset computers it will not necessarily keep the transient voltage spike to a level that is safe for the electronics. The transient surge may actually destroy the capacitor.

A diode on the other hand will dissipate the coil's energy quickly and keep the voltage surge to whatever the diode's foward voltage drop is (typically less than 1 volt).
User avatar
Dethrider
Apprentice
Apprentice
Posts: 12
Joined: Sun Feb 18, 2007 8:38 pm
Location: Stewartsville, NJ

Re: Has anyone done any of these track ideas?

Post by Dethrider »

Depends on coil type, AC or DC.

I have always used capacitors to remove the noise and never had one go bad. We are talking 240 volt ac coils to suppress EMF's for digital addressable network timer systems.
Brian Oshman
Doug-in-the-woods
Pine Head
Pine Head
Posts: 68
Joined: Mon Apr 02, 2007 7:28 pm
Location: Salmon, Idaho

Re: Has anyone done any of these track ideas?

Post by Doug-in-the-woods »

Have never seen a capaciator across a coil but if it works?
alwasy seen diodes but then again can on put diodes across an ac solenoid coil?
Post Reply