Landracing Forum
Tech Information => Technical Discussion => Topic started by: Jonny Hotnuts on July 13, 2008, 09:14:33 PM
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Last year I had a switch array:
(http://static.summitracing.com/global/images/prod/large/mor-74180.jpg)
I had all electrical components switched so I could turn them on an off separately (water pump, fuel pump, fans, compressor for shifter, and ignition).
The problem is that you had to turn everything on separately and in a certain order.....this also means that you could forget to turn on the water pump or fans (it happened in pits). My pop had trouble with the order and it was especially difficult when suited.
This year I installed a second high amperage battery disconnect on the dash, with a 4 gauge lead to a distribution block that turns everything on or off. Now all one has to do is turn on the on dash disconnect switch and push the start button. No chance to forget to turn something on or in the wrong order. The drawbacks are that you need a lot of battery to start the motor with all the crap running….you also cant run any of the systems separately if you wanted. We have a generator in the back of our tow truck with a massive battery charger and two Optima yellows so power is not a problem.
This annoyance seems like a small price to pay for the ease of a 1 switch does all setup.
Anyone else do this?
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In other forms of racing we use separate switches so we can isolate a circuit if it becomes necessary. We also use redundant circuits. Those systems probably aren't necessary in lsr as long as your fire system, chute system, etc. are manual and don't depend on electricity.
Pete
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My opinion only:
Since it's not good to run anything that draws amps directly through a switch, all switches can be armed in an IGN ON state only.
So you set all your switches in RACE MOD, but they need IGN ON to actually go hot.
This gives you a master kill, and avoids draining the battery, but still allows deselection of items like fans or fuel pumps. Just make sure that all switches are in the same direction for RACE mod. So a quick glance can tell you everything is armed.
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I agree with MCR.
These are all auxiliary systems(sometimes none are used, sometimes all are used.. and any combination inbetween).
All switches being used go forward when at the startline, all switches go rearward first chance after successfully completing shut down.
(http://i122.photobucket.com/albums/o244/narider/Maxton%20June%202008/102_0191.jpg)
There are a couple of the switches that perform dual duty as programming switches for some of the electronics. This allows adjustments without the safety concern of the starter or ignition systems, etc being live or accessable while doing so.
Blue painter's tape and a Sharpie (to make cheat sheets in our line of sight in staging to replace our memory) are the most valuable tools we've ever used on our vehicles, (thankfully Deb remembers to make sure the cheat sheets are on our bikes at each meet - lol).
Todd
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Since it's not good to run anything that draws amps directly through a switch
Any switched electrical device has some degree of amperage going through the switch, how much amperage is based on the device being run. Even if your dash switch operates a relay (relay is just a switch with a magnet) the current draw of the electrical device still passes through the switch.
I am just trying to figure out what you are meaning. I do like the idea of a master “on” and still have the ability to isolate things….maybe next year if I find I don’t like how it goes this year.
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Since it's not good to run anything that draws amps directly through a switch
Any switched electrical device has some degree of amperage going through the switch, how much amperage is based on the device being run. Even if your dash switch operates a relay (relay is just a switch with a magnet) the current draw of the electrical device still passes through the switch.
The switch that activates the relay only has the amperage needed to pull the relay in (milliamps), not that of the electrical device you are activating with the relay.
By the way.. the blue switches in Deb's dash above are rated at 40amps (as much as or more then the average 30 or 40 amp auto relay) :-o
I verified it by loading one up and it not creating an "imploding meltdown" :-D until I read 55 amps on the digital gage.
Todd
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You can pull quite a bit more current through a switch than it is rated for-- but it won't last long. In fact after a few on/off cycles you may find the contacts welded shut, just like a relay that is being used improperly.
The worst application for switches & relays is having a load that is a lamp or a motor. A lamp has a very high "inrush" current when the switch is turned on because its filament has a low resistance whan it is cold and an inductive load such as a motor or large solenoid generates a high voltage spike when the current is turned off. These can eventually destroy the switch contacts.
Switches and relay contacts have a current rating that should not be exceeded. In addition the contacts have AC & DC current ratings which may be different. This depends on the metals in the contacts.
Don't go to Radio Shack for the switches in your race car.
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From an aerospace EE: Relay contacts are no more reliable than switch contacts of equal ratings.
If we don't need separate controls, go with the single switch and separate circuit breakers for the individual systems. Many modern motor sports power distribution systems do this. One button on, breakers for faults.