Electronic Interference Prevention

Discussions on buying or building timers, solenoid start gates, light trees, weigh scales, and other race related electronics.
Post Reply
User avatar
gpraceman
Site Admin
Site Admin
Posts: 4607
Joined: Fri Jun 20, 2003 12:46 am
Location: Highlands Ranch, CO
Contact:

Electronic Interference Prevention

Post by gpraceman » Mon Feb 12, 2007 8:58 pm

There have been cases of electronic interference causing problems with electronic timing systems. Timing systems run on low voltage DC and higher voltage circuits and cabling can induce extraneous currents in those systems leading to strange results. Some people have also experienced power fluctuations that have caused abnormally low race times.

Here's some prevention measures:

1) Check your power connections (to the wall outlet, to the timer and anywhere in between). If you wiggle them, the timer's display should not flicker.
2) Plug the timer’s power supply into a power strip with a built-in surge suppressor. Better yet, use a UPS (Uninterruptible Power Supply).
3) Make sure that you do not run the serial cable or the start switch cable next to any extension cords. Run the serial and start switch cables on one side of the track and any power cords on the opposite side.
4) Keep any solenoid start gate circuit separated as far as practical from your start switch and cable.
5) Never run an extension cord under an aluminum track.
6) Any piece of equipment that cycles on/off should be turned off during the race.


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.

Doug-in-the-woods
Pine Head
Pine Head
Posts: 66
Joined: Mon Apr 02, 2007 7:28 pm
Location: Salmon, Idaho

Re: Electronic Interference Prevention

Post by Doug-in-the-woods » Wed May 16, 2007 4:56 am

ferrit coils and or just looping cables a couple of loops will cancle out most if not all interference.
But running ac cables away from dc cables will help.



User avatar
gpraceman
Site Admin
Site Admin
Posts: 4607
Joined: Fri Jun 20, 2003 12:46 am
Location: Highlands Ranch, CO
Contact:

Re: Electronic Interference Prevention

Post by gpraceman » Wed Mar 09, 2011 10:19 am

The above list has been updated to include power fluctuation issues. I have seen some cases of power fluctuations causing timers to have abnormally low race times for some of my software customers.

I even experienced it myself for one race that I ran for a church a couple of years ago. The cause turned out to be a lead melting pot in the pit area. When the heater element turned on, it would cause a power fluctuation with the timer as they were plugged into the same outlet. Unfortunately, I didn't discover the source of the problem until the next year that I ran the race for this same church and saw the melting pot over in the pit area. I do now make sure that church turns off the melting pot before we start racing.


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.

User avatar
Duane
Master Pine Head
Master Pine Head
Posts: 149
Joined: Mon Feb 01, 2010 11:25 pm
Location: San Jose,CA

Re: Electronic Interference Prevention

Post by Duane » Wed Mar 09, 2011 11:22 am

In Arduino-based timers, it will be easy to power all the electronics off of the laptop and its battery, using just the power line in the USB cable. That would give total isolation from the venue's AC power fluctuations, and any molten-lead pots, lefse grills, beer chillers, or whatever.

Another possible source of interference is induced currents in the long run of wires to an optical start gate sensor. Problems there can be avoided by using twisted-pair telephone wire rather than plain straight wires.



User avatar
gpraceman
Site Admin
Site Admin
Posts: 4607
Joined: Fri Jun 20, 2003 12:46 am
Location: Highlands Ranch, CO
Contact:

Re: Electronic Interference Prevention

Post by gpraceman » Wed Mar 09, 2011 11:39 am

Duane wrote:In Arduino-based timers, it will be easy to power all the electronics off of the laptop and its battery, using just the power line in the USB cable. That would give total isolation from the venue's AC power fluctuations, and any molten-lead pots, lefse grills, beer chillers, or whatever.
True, but I always run my laptop off of the power supply. I'd hate to have my battery die in the middle of a race.

beer chillers :lol: Must be a redneck race.


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.

dna1990
Master Pine Head
Master Pine Head
Posts: 360
Joined: Wed Jan 09, 2008 9:16 pm
Location: Houston, TX

Re: Electronic Interference Prevention

Post by dna1990 » Thu Mar 10, 2011 10:36 am

Duane wrote:Problems there can be avoided by using twisted-pair telephone wire rather than plain straight wires.
Agree, but be sure to ground any un-used pairs in the cable.

We went this year with CAT5 cabling from the head of the track down to the timer. These cables carried the mech start switch, the DC power to the timer, the serial connection between timer/pc, and signals for our 'starter button'. This eliminated the need to run AC the length of the track, which I believe helps reduce chance of picking up some noise.

The serial signal is in one CAT5 cable, RX, Gnd, TX, Gnd, and Gnd, Gnd, Gnd, Gnd. Another CAT5 carries everything else. Makes setup much easier, everything color coded, etc.



msurebel
Journeyman
Journeyman
Posts: 31
Joined: Tue Nov 08, 2011 8:05 am
Location: Olive Branch, MS

Re: Electronic Interference Prevention

Post by msurebel » Wed Jan 18, 2012 12:19 pm

I was planning on using a cat5 cable to route all my sensor and start gate trigger to avoid the seperate cables for each. I've even thought of running two sets of cat 5, with one of them providing power for the start gate. At the moment, it's way down on my list of things I have to get done. :whew:



User avatar
gpraceman
Site Admin
Site Admin
Posts: 4607
Joined: Fri Jun 20, 2003 12:46 am
Location: Highlands Ranch, CO
Contact:

Re: Electronic Interference Prevention

Post by gpraceman » Wed Jan 18, 2012 12:37 pm

msurebel wrote:I was planning on using a cat5 cable to route all my sensor and start gate trigger to avoid the seperate cables for each. I've even thought of running two sets of cat 5, with one of them providing power for the start gate. At the moment, it's way down on my list of things I have to get done. :whew:
IMO, it is better to keep these separated.


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.

msurebel
Journeyman
Journeyman
Posts: 31
Joined: Tue Nov 08, 2011 8:05 am
Location: Olive Branch, MS

Re: Electronic Interference Prevention

Post by msurebel » Thu Jan 19, 2012 8:06 am

Randy, are you saying to keep the start gate power seperate, or keep all the sensors seperate? I would think with cat5 having twisted pairs, it will negate any interference. Of course, I've never tested it. What's been your experience.



rpcarpe
Master Pine Head
Master Pine Head
Posts: 734
Joined: Wed Mar 17, 2010 11:58 am
Location: Huntsville, Alabama

Re: Electronic Interference Prevention

Post by rpcarpe » Thu Jan 19, 2012 9:37 am

Randy,
Thank for the reminders as we head into the weekends of many derbies!
I just previewed the layout of our derby, and will keep this things in mind.


My wife started a new support group... Widows of the Pinewood Derby.

User avatar
PeterT
Pine Head
Pine Head
Posts: 60
Joined: Wed Dec 21, 2011 10:53 am
Location: Pittsburgh area, PA

Re: Electronic Interference Prevention

Post by PeterT » Thu Jan 19, 2012 10:09 am

good tips - we use "the judge" and have always used it battery powered, so I think it will stay that way due to power isolation issues. We intentionally have the finish line in the middle of the room with absolutely no computer around. Thanks to the batteries we have three lines running back: regular audio cable type wires to the start gate, same type of cable running to the computer near the start line (via a serial-usb connection), and an active usb extension cable running from the finish line camera to the same computer.

The CAT5 connection sure would be near, but for the past three years we've had zero problems with timing so I think for us I will leave it alone.

For anyone else with an older "The Judge" (ours is ~14 years old): we sent ours back to the manufacturer two years ago and he rebuilt it to current specs. Cost was something like $40 and all of our problems went away. Well worth it!



User avatar
gpraceman
Site Admin
Site Admin
Posts: 4607
Joined: Fri Jun 20, 2003 12:46 am
Location: Highlands Ranch, CO
Contact:

Re: Electronic Interference Prevention

Post by gpraceman » Thu Jan 19, 2012 10:30 am

msurebel wrote:Randy, are you saying to keep the start gate power seperate, or keep all the sensors seperate? I would think with cat5 having twisted pairs, it will negate any interference. Of course, I've never tested it. What's been your experience.
I just prefer to keep anything related to the solenoid circuit separated from the start switch, timer circuit and computer cabling, as triggering the solenoid can cause a surge.


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.

msurebel
Journeyman
Journeyman
Posts: 31
Joined: Tue Nov 08, 2011 8:05 am
Location: Olive Branch, MS

Re: Electronic Interference Prevention

Post by msurebel » Thu Feb 16, 2012 6:26 pm

Could a large amount of cell phones cause problems? I and another pack have had similar problems of having everything working the night before the event and then the day of the event get crazy readings. We made sure everything was the same. Amps mics, overhead lights, etc were the same. We don't think sunlight was the issue because we were no where near any. The only difference I can think of is 50-100 people with cell phones present during the race. Although we had the same make of timer, his was brand new. New bold, with the wires to the sensors being little more than speaker wire, I wonder if they could picking up interference from phones?



User avatar
gpraceman
Site Admin
Site Admin
Posts: 4607
Joined: Fri Jun 20, 2003 12:46 am
Location: Highlands Ranch, CO
Contact:

Re: Electronic Interference Prevention

Post by gpraceman » Thu Feb 16, 2012 6:35 pm

msurebel wrote:New bold, with the wires to the sensors being little more than speaker wire, I wonder if they could picking up interference from phones?
I really doubt that is possible.


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.

Post Reply