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longtime no see.. good to be back!

Posted: Wed Dec 17, 2014 8:04 am
by pack529holycross
Been a while since Ive visited, and enjoying the refreshing of my memories from previous years. I am in a new part of Orlando this year, the last year of my Sons Cub Scouting Program .. :/
The Pack he is finishing up with has a more basic track - haven't seen it yet, but going to assume there isn't a timer able to be attached to the gprm software for projection. What is the current lay of the land for basic timer investment that doesn't require a separate dispay on the timer itself, and still maintaining highest reliability?

Im seeing a 4 lane k1 kit for $135 + $60 for the start switch and cpu kit. Im considering just buying myself a timer to have on hand in situations where packs who want derby assistance don't have their own timer. It will also be helpful for derby construction seminars I teach at University of Scouting.

Anyone able to recommend alternative candidates for $195 or under for 4 lanes that match the reliability level?

great to be back amongst my "peers"

Nicholas

Re: longtime no see.. good to be back!

Posted: Wed Dec 17, 2014 9:03 am
by gpraceman
Welcome back Nicholas.

If you want a timer for less than $195, there is the NewBold DerbyStick. The drawback of such a timer is that it has no finish order display, so you must use a computer with it and hope that you do not run into communications issues on race day. It also needs you to provide an incandescent light source for the sensors.

There is also the Microwizard K1 cheap kit with computer interface for $65. You have to solder together the components, build a housing for the electronics and come up with your own start switch. For $20 more, they will do the soldering for you.

If you are willing to do more of the construction, there is always the Yet another Arduino based track timer.

Re: longtime no see.. good to be back!

Posted: Wed Dec 17, 2014 9:41 am
by pack529holycross
I did see the Stick.. my question has always been what is the accuracy and reliability comparison between led and "provide a light source" sensing systems?

Re: longtime no see.. good to be back!

Posted: Wed Dec 17, 2014 9:51 am
by gpraceman
pack529holycross wrote:I did see the Stick.. my question has always been what is the accuracy and reliability comparison between led and "provide a light source" sensing systems?
I don't know that anyone has really done that type of analysis on accuracy, other than the manufacturers themselves.

On reliability, much depends on providing enough light to each lane sensor. Some have run into problems with that issue. You may need to use multiple incandescent lights. Personally, I'd rather have the light source built into the timer and not have more gear to haul and store away.

Re: longtime no see.. good to be back!

Posted: Wed Dec 17, 2014 7:37 pm
by Stan Pope
An issue I've seen (yes, actual pack and district racing) with "independent light sources" is that the "shape" of the light source interacts with the shape of the car's front end and determines the line crossing time "somewhere close" to the actual crossing time. To understand this point, visualize a light source in a 12" diameter reflector positioned 12" above the finish line.

Consider that part of the reason for having a 12" reflector could be the need for ALL of that light to operate the photodiode. So a car, L, with a 3/8" high front end runs against a car, H, with a 1" high front end. Both cars impinge on the light cone before they reach the actual finish line. Car H impinges further up track! So Car H would win if the two cars crossed side-by-side.

On the other hand, the photodiode might trigger only if ALL of that light is masked. In this case Car L would win if the two cars crossed side-by-side. Worse, if one of the cars had a front end with a smallest dimension of 1/4", e.g. a 1/4" diameter bar across the front of the car, then the car may not even trigger the photodiode.

Re: longtime no see.. good to be back!

Posted: Sat Jan 10, 2015 4:12 pm
by craig_newbold
Hi Guys - thought a little follow-up info was warranted on this topic. We have a new product just out that is designed to work with DTX000, Turbo Lite, and DerbyStick products.

The LightBridge uses IR light sources centered over each lane to illuminate the IR detector mounted in the track below.

http://www.pinewood-derby-timer.com/cat ... 144436.htm