# 10 amp Direction switch.



## Ovalhead (Nov 20, 2010)

On the Trackmate Drivers Stations panel, it has a lane direction horizontal slide switch. The manual states it is a 10 amp Direction switch.

What does this tell me ? OR SHOULD I ask, will it work with a 20 AMP variable PS ?

I is he, the yahoo who always gets shocked...............

Thanks in advance,

Cliff


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## AfxToo (Aug 29, 2003)

This is a very smart question to ask because you are thinking about the electrical system as a whole. The "system" that we care about in this case is the over-current protection system. You want to make sure that you both supplying enough current to support the total need but are not allowing excessive current to be applied to any individual electrical component in the circuit. One of these components is the 10 amp direction switch. But there are several others, like your controller, the track wiring, electrical connections, track power relay, and of course the cars themselves. In fact, the most vulnerable component is probably not the direction switch. It's unlikely that your controller or a car would be able to handle even 10 amps before being permanently damaged so you should be thinking about protecting other things that have even lower current handling capabilities than the switch. 

So the conditional answer is yes that 10 amp switch is safe to use with a 20 amp power supply present but only if you guarantee that you will never have more than 10 amps going through the direction switch. You do this by having a current protection device in the circuit feeding the direction switch. A fast acting fuse rated for no more than 10 amps would do the trick. Alternatively you could use a DC circuit breaker. If you go with a DC circuit breaker you should derate it to something less than 10 amps (say 5 amps or 7 amps) because circuit breakers do not trip instantly. Circuit breakers act more like slow blow fuses which means they will handle the maximum current for some period of time before they trip. Some electrical devices, like the direction switches, are able to handle brief over-current situations better than others. Controllers and motor windings are much more likely to be damaged than is the switch so even 10 amps may be far too much.

I took a look at the drivers stations on the TrackMate site (nice!) but I can't tell whether they have a fuse or circuit breaker in their design. They tend to do high quality work and well engineered designs. The fact that there is a fault LED tells me there is some sort of protection device like a self resetting circuit breaker in their design. You should ask them about it and I'm sure they will give you all the details.

When you are designing your own electrical system for your track it's always smart to think about the whole supply and over-current protection system from end to end and in a systematic way. In this case you have a 20 amp power supply, which is a pretty stout power source for any class of road racing on a 4-lane track. You want all that power available to the track but you don't want to burn anything up. The first thing to consider is protecting the power supply itself and then move on to every component in the electrical circuit to ensure you are never allowing more current to be supplied to a component that it can handle.

1) What do you have to do to protect the power supply itself? You may want to know whether the power supply has built-in over current protection. What kind of protection does it use? If it uses a crowbar circuit this means that when it senses a short circuit it internally shunts all current and the output current goes to zero. If it uses a clamp circuit it means that when it sense a short it clamps the output current at a fixed non-zero level up to the maximum level, which is 20 amps in this case. Or it may have no internal protection. The safest practice here, especially if you don't know, is to put a fast acting 20 amp fuse on the main feed from the power supply to the track. This means that all 20 amps are available to the track as a whole but if something happens, like a short circuit in the wiring to the track, the power supply is protected. Of course this assumes that the wiring from the power supply to the track can handle 20 amps. If you do something silly like use 22 awg wire the wiring will melt before the fuse blows. Take a look at this chart: http://www.seas.gwu.edu/~ecelabs/appnotes/PDF/techdat/CCCofCC.pdf and you'll see that the power supply to track wiring should be at least 14 awg if you want to handle 20 amps. 

===> If you undersize your wiring you'll need to lower your fuse rating to protect the wiring instead of protecting the power supply.

2) Once you have protected your power supply (and wiring) you'll need to move on to anything between the power supply and the your drivers stations. If you have any electrical components like a track power relay in the the circuit you'll need to know the maximum current capacity of these. Relays always have a maximum current rating for their switched contacts. If you can supply 20 amps to the track make sure your track power relay can handle at least 20 amps. If it cannot, you'll have to lower your fuse rating to protect the track power relay. 

3) Once you know you are protected for the weakest link in your power supply, wiring, and track power relay you'll need to move on to each of your drivers stations. If you have any electrical components in your drivers stations other than wires, things like potentiometers, voltage dropping diodes, switches, relay contacts, etc., you'll need to know the maximum current capacity of each of these. However, once you are looking at the drivers stations you are now talking about protecting each of these individually. You don't want to limit the TOTAL current supplied to the track to protect a drivers station because the total current is shared by all drivers stations. For example, if a drivers station could only handle 3 amps and you put a 3 amp fuse on the output of your power supply, you would be popping these like crazy. Therefore each of the drivers stations has to protect itself while not limiting the total current that can be supplied to the track.

If you want a better description I recommend the Siberia Racing web site. Steve has a great handle on wiring and provides excellent advice.


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## Ovalhead (Nov 20, 2010)

AfxToo, good morning, not sure which one of us woke up at the Holiday Inn Express, and that don't even matter. 

Thanks for taking the time to explain to me the system, and how it's supposed to work. I'll call Trackmate now, cause now I can act like I know what I'm talking about, kinda.

Will report back later with their low down on this. I might have to drop down to 10 a amp PS. ?

Have a great day,
Cliff


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## Hornet (Dec 1, 2005)

The little tan looking thing on the backside of the drivers panel,i think is a fuse.
Knowing Dan,it'll probably be one of the 5 amp self re-setting electronic fuses he sells.
Good post AFX
Rick


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## Ovalhead (Nov 20, 2010)

Just talked to Daniel @ Trackmate. He said my 30v 20a Mastech will work just fine with his panels and relays. He said I shouldn't worry unless I hook it up to 40 amps or more. He said the 20a will only push 5 amps per station and they are fused for 10 amps. 

Everything he told me 2 years ago about my Trackmate scoring system has been 100% on the mark, not one issue. So I ordered a few more electrical goodies also. 

I love good customer service, 
Cliff


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