4 Lane pinewood derby timer

[Jake 24]

I am going to try to pull this off!  I have 5 weeks to get it done.  This is for the elementary school that my kids go to, there all getting involved in getting the cars, track, and timing system all done. 

 

I was initially thinking a MSP430G2553

 

The controller would be able to

 

Drop starting gate and start timing with a pushbutton

( I really want to do a drag race light tree, but I may be getting too ambitious)

 

Record the time of each lane and write to display

 

Lane lights to light up winner lane.

 

I know I could build the lane win lights easily with components, but I am hoping to pull off the timing and display to screen.  Something simple like print to cmdline screen or the UART interface in CCS. 

 

 

Sooo do yall think I am out of my mind trying to go with this approach or? 

 

 

 

I am thinking the lane sensors would just be photodiodes in the track, sending inputs back to the controller

 

A Button input that will trigger the timer to start, and output to drop the start gate

 

Capture the time of each lane upon a change in state of the input pin, stop timer on the input of the last pin.

 

Thanks!

[cde 334]

You seem to have the general idea down. You could try adapting any number of arduino based Derby timers, like http://www.miscjunk.org/mj/pg_pdt.html with Energia, or start from scratch.

 

You could easily use two msp430 chips if its too big for one. Like, off load the gate and drag race light tree to one msp430, and then do all the time keeping and displaying on another.

 

Like Press Button on 430 A, A Lights tree, A drops gate, A toggles gpio of B, B starts timing, reads race times, displays on LCD or LED Matrix or sends via UART to computer or bluetooth.

[Jake 24]

thanks for the link!  I could use an Arduino also, I am going to try with the MSP first, that is a good idea with using two of them.  The displays take up a bunch of pins, that was one reason I was thinking about using the UART and going back to the PC to save some pins.  I am going to get rolling on it next week. 

[abecedarian 330]

Thinking about things... G2553....
Two pins for power / ground.
Two pins for watch crystal.
One pin to sense the "start" switch signal; doubles as reset after a race is complete.
One pin to control the "launch" gate solenoid.

Given 4 lanes:
One pin for each lane finish line detection... so 4 pins. May be photo diode or even reed switch.
One pin for each lane "win" LED... 4 pins; doing double duty to control the start line tree.

Two pins for I2C display, multiple I2C displays could share pins if they have separate addresses.

16 pins used out of 20 available.

You could use the remaining pins to implement your tree. If a pin is high, the tree is lit and you'd use the lane lights to simulate the tree, and if it's low, the finish line lights are active to show the winner. Tree could be red, red, yellow, yellow and then green with the other pin holding the green light on the tree after the tree is switched off by the other pin so it can control the lane lights.

Seems doable, even with Energia.

[cde 334]

Well if you go with i2c displays, you might as well use a i2c port expander or led driver for the Light Tree. Simpler than multiplexing or anything.

[Jake 24]

I'll be working on it next week! Do y'all have any good sources on the i2c displays?

 

Sent from my XT1254 using Tapatalk

[Fmilburn 446]

Addicore has reasonable prices, they ship the same day, and I have never had a problem.  They sell a 16x2 and a 20x4 and I have used both with Energia.

 

EDIT:  Should also note they are located in the US so delivery is pretty fast in the States...