THSCC Forums

I wanted to let everyone know what happened on Sunday, in case anyone is interested. In general we found ONE inherent weakness in the wireless, but this was solved before we got to the site. The downtime was all power related, and the result of human (me) error...

First -- at about 6:30 AM when I was packing up to leave (and already late!) I was unplugging the wireless Rx (receiver) when Jason called me on my cellphone. Being tired, and it was dark in the garage, my hand slipped when answering the phone and I DROPPED the receiver onto the concrete floor. I picked it up and hit Power and IT WOULDN'T TURN ON. Much swearing commenced on the phone to Jason. I told him I wasn't leaving until I fixed it. And I had the key to Sanford.

Slowly got it apart and started replugging connectors. Turns out that there is a flaky 4-position flex cable from the front panel which plugs into a boardmount ZIF. This must have moved just enough to cause it to lose contact. Also, the locking tab on the ZIF wasn't engaged, which was possibly not engaged from the factory. So I got it back together, all was well, and I drove 90 MPH to Sanford.

So that's why I was late!!!

LESSON: Don't drop the timing equipment (DUH).


And next up is the power situation on the transmitter (Tx)...

First a brief description of the transmitter: The sealed transmitter box which mounts on the bucket hight on the pole actually has an internal battery and takes only a simple 2-plug input from the laser head. The silver briefcase is used for storage of the Tx, contains the battery to power the laser head, a conversion circuit to change the signal from the laser head to the correct Tx input, and a status light box that Gordon designed to blink LEDs depending on the status of the laser head.

The power problems on Sun actually happened because of a string of errors dating back to when I first built the box. Let me start by saying that the wireless itself was actually working GREAT -- it was power to the LASER HEAD that was causing the missed finishes!

Here's a summary:

- I built the box with an internal battery, solar cell, and an external power switch. Plan was to never need to charge it
- The power switch was too easy to flip, and several times the box got turned on when loading it into the trailer earlier this year, draining the battery
- When Tx was needed and the battery was dead, we used jumper cables to a battery. As SOME POINT the + and - leads on the internal battery got REVERSED!
- Sat at setup we tested the wireless with the jumper cables and everything was working GREAT. Thought all would be well.
- On Sat PM I corrected the jumper cable hack -- wired in a charging plug (lightr adapter) to connect the internal battery to an external one -- so we wouldn't have to use jumper cables.
- On Sat PM I connected the power plug to the big yellow battery to charge the internal battery. It was late and I had stuff to do, so I never checked to see if/how well the internal batt was charging.
- On Sun AM I packed it all up, went to the site, and connected the supposedly-charged Tx system. The timer worked fine in testing so I assumed all was well.
- Partway through the first heat we started losing signals. We all immediately assumed it was a range problem and indeed we chased this for almost an hour.... It wasn't
- First I plugged in a fresh charged yellow battery using the new power plug I had wired in to give (I thought!) the suspect internal battery full juice ... this didn't solve the problem.
- We added extra cables to get the Tx closer to the bus and noticed a weak laser beam. Rather than, oh, maybe suspect the power (it had a fresh Optima connected!), I thought we had a bad cable or laser. After several swap-outs, someone had the bright (pun) idea to direct-plug the laser to the silver briefcase, and -- WOW -- Weak laser beam. Power problem.
- Finally direct-connected the leads to the battery posts (bypassing my lighter plug) and it worked fine. So we brought the jumper cables back out, connected them up, and Viola -- ZERO timer glitches for the rest of the event.
- Once we figured out that the laser wasn't getting power, I grabbed the ligher plug, unscrewed the tip, and found a blown fuse. Hadn't considered that there may be a fuse in there. Dumb.

So in retrospect, the fuse probably blew when I plugged it into the battery on Sat PM to charge it. So the internal battery (which was wired in backwards before charging) probably never charged. It's amazing that it was working at all on Sat AM with barely any power...

So needless to say, Version 3.0 of the wireless is coming soon. I'm ditching the bad (inside the sliver case) internal battery and solar cell, and setting it up to direct-connect to the Optima. Then all we need is a small waterproof case for the signal converter, a plug for the laser, and connectors for a cable to the Tx.

The design will be simpler, but the setup will be more complex because of the car battery -- but now I know that sometimes more work in a robust system is preferable to an elegant solution which is fragile.

_________________
Mike Whitney
whit32@gmail.com, 919-454-5445
V10, V8, V8t, I6, I6, V6, F4t, I4, I4, I4, I4, I2, 1, 1

cool, sounds pretty slick. maybe a charger meter or just a power bulb (not led, so it can fade w/ power level) would be handy.

let me know if you ever need extra hands. making wires in boxes do cool things is my forte

Dan -

I need to find a waterproof box/enclosure, probably 6"x6"x2". Plastic or something easily machinable would be best -- plan to have some cables coming out, a few switches and some LEDs.

Any ideas?

Also if you're near Cary and want to drop by this weekend I'd like to bounce some ideas off you about how to implement the new, simple version... Let me know if you'd like to get involved.

_________________
Mike Whitney
whit32@gmail.com, 919-454-5445
V10, V8, V8t, I6, I6, V6, F4t, I4, I4, I4, I4, I2, 1, 1

sure. i'll be out of town this weekend, but maybe some other time (i live in cary).

http://www.hammondmfg.com/scpg.htm

i've only used Hammond's metal boxes before, but they have some nice looking watertight plastic ones too. i see a few that are ~6x6x2"

i normally use www.mouser.com for switches, connectors, LEDs, etc, etc. they have it all and ship really fast.

if you have time, maybe you can email me a drawing or schematic of what is going on here. it does sound like fun!

Pelican makes all sizes of waterproof plastic boxes, check with some of the dive shops around here to see what they may have in stock.

_________________
SPIN or WIN!
there's no glory for going slow.

Thank for only posting the summary explanation

You know, if you use a Tupperware container, then if you need to open it to service something inside, you just pop the lid. Also, if you drop it, the plastic is flexible, so it absorbs some of the shock. And the circuitry always stays nice and fresh.

Seriously, thank you again for engineering this thing. Next, would you come up with a giant conveyor to haul coursewalkers quickly from the finish line to the start line?

Acutally, that reminds me. There was a white pickup with an extended cab that ferried me TWICE from the finish line to where I parked after course walks. MANY THANKS!!!!!!!

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Beauty is in the eye of the beer holder.

I think that might have been Dan Bishop, he has a silver Dodge Ram (for sale if anyone is interested:) ). A relatively new member of THSCC. He was also the one who volunteered his truck when it looked like we might need to raise the transmitter above the cars.

Dan's a good guy and probably a DSM to Miata convert much like Ryan!!

_________________
Todd Breakey
STS 42 - 1992 Sunburst Miata
Dammit!
"You souldn't play leap frog with a porcupine. You might get hurt." - Eliza

Well I have to say it is nice to be able to drive a car that actually runs. And as for the selling of the truck......we will see.

Mike, back when I was putting together the microprocessor signal conditioner for the wireless transmitter, I ran some data sheets for C-cell and D-cell batteries. The power drain on the laser head is much less than you would expect (less than 20mA, if I recall correctly), and a stack of eight plain old alkaline batteries should power it for several days. This is one alternative to having to trot out a heavy car battery and remember to recharge it between events. At the very least, it would be good to keep around a set of alkalines to use as an emergency backup.