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DPST large momentary push button.
bobinspain - 26/6/12 at 05:08 PM

There's such an item on ebay which is rated at 16a 240v a/c.
I need a double pole single throw (DPST) which is ideally rated at 40-50a and 12v d/c and can't find one.
I have the a/c version fitted to my Busa and the two circuits simulataneously operate the starter motor and the clutch-position-indicator circuit. I encountered a problem yesterday which may be down to 'splashing' of the contacts which produced the short I experienced.
I have the 'gated' aircraft toggle switch for power-on/off and the push-button for starting. I was taken aback yesterday, when on operating the toggle switch, (without touching the push-button), the engine fired into life.
Turns out there's a short on two contacts of the DPST push button. I switched off and removed the switches and by easing (with pliers) the spade contacts broke the short, but I'm afraid it may happen again, and a permanently made staarter-motor circuit wouldn't be healthy.
Any ideas where I can get the correctly rated d/c DPST momentary push button guys?
I know watts=amps x volts and just using the numbers, the a/c switch would appear man enough for the job, (16a x 240v versus 50a x 12v for the d/c switch--if I could find one).

owelly - 26/6/12 at 05:13 PM

I may have missed the point somewhere, but could you not use a pair of heavy duty relays or solenoids operated by the low current switches?

Stott - 26/6/12 at 05:23 PM

What he said ^^^^^

The reason it's difficult to find a 50a rated momentary push button is that no one wants to make and break that current with a switch.

Just use the starter solenoid off the bike and you can use a replacement switch identical to the one you already have.

Quite why it was left out and they chose to directly switch the starter is a mystery.

Unless, your understanding is that as it's the starter then it's switching a high load but in actual fact it was just a crap switch. In which case get any quality replacement that fits the hole.

snowy2 - 26/6/12 at 05:49 PM

They sell a switch like your description in a shop called “The Range“ of all places for about a fiver!

bobinspain - 26/6/12 at 07:06 PM

I have probably misled you chaps. I didn't give the whole story because I thought I bore tha pants off you.
If you check out an old thread of mine 'Busa FI light' then you'll have the history.
MK use an electro-hydraulic clutch-position-indicator switch. The relative slowness of this switch to operate triggers the FI light on the Hayabusa internal diagnostics. This flags a problem (by illumination of the FI light) that doesn't exist.
A way around the problem is to replace the electro-hydraulic switch with a pure electrical switch, (DPST).
I want a single button to do the job and it must be as aesthetically correct as the button it replaces. (Aero and slick looking). If you take a look at the second photo in my archive, you'll see what I'm replacing.
I can use a functional double switch arrangement, yes, but it's not really an 'elegant' solution.

Snowy, I'll check out the Range. Thankyou.

big-vee-twin - 26/6/12 at 07:15 PM

Think you need one of these Chrome Engine Start Starter Push Button Power Switch - Full kit with loom! | eBay

You will need another relay in parallel with the one in the kit

[Edited on 26/6/12 by big-vee-twin]

bobinspain - 26/6/12 at 07:26 PM

quote:
Originally posted by big-vee-twin
Think you need one of these Chrome Engine Start Starter Push Button Power Switch - Full kit with loom! | eBay

You will need another relay in parallel with the one in the kit

[Edited on 26/6/12 by big-vee-twin]




Thanks for the suggestion.
Regrettably, the ad' states it's a two wire system ie single function. That's precisely the button I removed from my factory build in order to fit a double-pole, double function switch.
I want a twin function with one button if at all possible and don't want a separate relay. It'll look 'gash' and too busy along with the toggle switch.
Surely there must be someone who supplies a d/c DPST?

gremlin1234 - 26/6/12 at 07:34 PM

quote:
Originally posted by bobinspain

I know watts=amps x volts and just using the numbers, the a/c switch would appear man enough for the job, (16a x 240v versus 50a x 12v for the d/c switch--if I could find one).


amps (not total power) are the important thing on switches,
also dc switching will normally only be rated 10-50% of an ac rating.
common mode of failure is the contacts weld themselves together

Paul_C - 26/6/12 at 07:43 PM

Just to agree with gremlin1234. The switch AC current rating relies on the current dropping to zero 100 times per second to break the arc. DC is considerably harder to turn off so the switch DC current ratings can be lower independent of voltage.

owelly - 26/6/12 at 07:44 PM

I still don't understand why you can't use two relays as it would be just the same as having a DPST switch. You can hide the relays wherever you want and you'll just have whatever switch that matches your dash.

Stott - 26/6/12 at 07:44 PM

I still don't get why you need to switch circa 50A though, a wiring diagram would help

bobinspain - 26/6/12 at 07:46 PM

quote:
Originally posted by Stott


Unless, your understanding is that as it's the starter then it's switching a high load but in actual fact it was just a crap switch. In which case get any quality replacement that fits the hole.




You may well have hit the nail on the head Stott. It's a cheapo switch, since it's the only one I could find that was double-pole. The single-pole original starter button was a quality item. I 'cured' a constant FI light using this double-pole switch.
Long story on 'Busa FI Light' thread.

big-vee-twin - 26/6/12 at 07:59 PM

It seems very straight forward to me, you buy the switch you want, it doesn't need to be double pole and you use that to switch a double pole relay or two single pole relays rated at the required amps.

You fit the switch into your hole on the dash and hide the relays under the scuttle as previously suggested.

bobinspain - 26/6/12 at 08:01 PM

quote:
Originally posted by Stott
I still don't get why you need to switch circa 50A though, a wiring diagram would help



Stott,
As you may have gathered, I'm no spark!
I merely quoted 50amps as the average spec for a momentary push button starter switch as advertised on ebay.
The Gen 2 Busa clutch-position-indicator/sensor switch on the bike is electrical. My Gen 2 Busa MK Indy-R has an electro-hydraulic actuator for the clutch position-sensor which by it's nature operates slower than the bike switch and this causes the ECU to sense a problem related to clutch position which isn't a problem, but merely a 'slow' switch.
The solution to the above is to take the electro-hydraulic clutch-position-indicator switch out of the loop and replace it with an instantaneous electrical switch. The DPST (if it were D/C and man enough) would be a simple and elegant solution to solve the problem.
I tried it for 2 months, and it worked splendidly until yesterday.

loggyboy - 26/6/12 at 08:14 PM

http://www.maplin.co.uk/splashproof-push-switch-dpst-2345 ???

paulf - 26/6/12 at 08:45 PM

You dont need 2 contacts or 2 relays as i understand it.If a single pole switch is fitted then it can be used to supply the 12v signal for the clutch position and the same signal can pull in a basic single pole relay to operate the starter.
Paul

Stott - 26/6/12 at 09:09 PM

quote:
Originally posted by bobinspain
quote:
Originally posted by Stott
I still don't get why you need to switch circa 50A though, a wiring diagram would help



Stott,
As you may have gathered, I'm no spark!
I merely quoted 50amps as the average spec for a momentary push button starter switch as advertised on ebay.
The Gen 2 Busa clutch-position-indicator/sensor switch on the bike is electrical. My Gen 2 Busa MK Indy-R has an electro-hydraulic actuator for the clutch position-sensor which by it's nature operates slower than the bike switch and this causes the ECU to sense a problem related to clutch position which isn't a problem, but merely a 'slow' switch.
The solution to the above is to take the electro-hydraulic clutch-position-indicator switch out of the loop and replace it with an instantaneous electrical switch. The DPST (if it were D/C and man enough) would be a simple and elegant solution to solve the problem.
I tried it for 2 months, and it worked splendidly until yesterday.




In that case I'd say get another double pole switch and replace it.

Strange thing is when you threw the toggle on to make the ignition live, if the starter switch contacts had welded shut then the car still shouldn't have cranked over due to the clutch switch side of it being open. It sounds more like the switch actuator was internally jammed somehow but anyway.....

The savage switches a lot of us use on here have an engine start button in the range. LINK HERE

They are made by apem and from memory have enough contacts on the standard switch block to do 2 pole switching either normally open or normally closed.

This switch will be rated highly enough to switch the starter solenoid and the clutch switch override, and it's made by apem - a quality manufacturer.

You can get the led's to change the illumination colours too


HTH
Stott

gremlin1234 - 26/6/12 at 09:10 PM

quote:
Originally posted by paulf
You dont need 2 contacts or 2 relays as i understand it.If a single pole switch is fitted then it can be used to supply the 12v signal for the clutch position and the same signal can pull in a basic single pole relay to operate the starter.
Paul

indeed a single relay should suffice, though I would use the original switch to control the starter, and a slave (relay) for the additional circuit.

bobinspain - 26/6/12 at 09:29 PM

quote:
Originally posted by Stott
quote:
Originally posted by bobinspain
quote:
Originally posted by Stott
I still don't get why you need to switch circa 50A though, a wiring diagram would help



Stott,
As you may have gathered, I'm no spark!
I merely quoted 50amps as the average spec for a momentary push button starter switch as advertised on ebay.
The Gen 2 Busa clutch-position-indicator/sensor switch on the bike is electrical. My Gen 2 Busa MK Indy-R has an electro-hydraulic actuator for the clutch position-sensor which by it's nature operates slower than the bike switch and this causes the ECU to sense a problem related to clutch position which isn't a problem, but merely a 'slow' switch.
The solution to the above is to take the electro-hydraulic clutch-position-indicator switch out of the loop and replace it with an instantaneous electrical switch. The DPST (if it were D/C and man enough) would be a simple and elegant solution to solve the problem.
I tried it for 2 months, and it worked splendidly until yesterday.




In that case I'd say get another double pole switch and replace it.

Strange thing is when you threw the toggle on to make the ignition live, if the starter switch contacts had welded shut then the car still shouldn't have cranked over due to the clutch switch side of it being open. It sounds more like the switch actuator was internally jammed somehow but anyway.....

The savage switches a lot of us use on here have an engine start button in the range. LINK HERE

They are made by apem and from memory have enough contacts on the standard switch block to do 2 pole switching either normally open or normally closed.

This switch will be rated highly enough to switch the starter solenoid and the clutch switch override, and it's made by apem - a quality manufacturer.

You can get the led's to change the illumination colours too


HTH
Stott


I thought that about the clutch side being open too. ??
I have all savage switches for all other electrical switching. I'll have a look online to see if I can get the job done with one.
I have indeed ordered another DPST Momentary Push Button from ebay on the off-chance the first one was faulty. I intend sacrificing the one on the car to perform an autopsy to determine the cause of the fault.
Thanks to all for the steers.

Bob.

owelly - 26/6/12 at 09:29 PM

Excuse the crappy drawing but I'm limited when using a phone to browse!
I still can't see where the problem is. The top of the piccy shows a momentary DPST switch. And uder it, a SPST momentary switch operating a DPST relay which can be as heavy as you like. You could even have the SPST switch operating a pair of SPST relays which would do the same job.

Stott - 26/6/12 at 09:38 PM

The thing is the starter circuit has already got the starter solenoid which is probably off the busa, similar to my gsxr one, so the car is already wired to switch the low current side for the starter circuit.

As for the clutch switch it's a simple open or close to earth number on the bike, very low current and doesn't warrant a relay or anything.

So in this scenario, a DPST switch is the simplest way of doing the job.

I think the confusion here stems from post 1 where bob was a bit confused as the the loading he required to switch.


atb
Stott

bobinspain - 27/6/12 at 08:29 AM

quote:
Originally posted by Stott
The thing is the starter circuit has already got the starter solenoid which is probably off the busa, similar to my gsxr one, so the car is already wired to switch the low current side for the starter circuit.

As for the clutch switch it's a simple open or close to earth number on the bike, very low current and doesn't warrant a relay or anything.

So in this scenario, a DPST switch is the simplest way of doing the job.

I think the confusion here stems from post 1 where bob was a bit confused as the the loading he required to switch.


atb
Stott


Stott you're right. I was under the impression that most starter buttons (ebay listed ones anyway) were rated at 30-50amps D/C. and since I had fitted a 16amp (240v) A/C push-button starter then it was that which had caused the short. Equally, your assertion that the DPST switch was "the simplest way of doing the job" is why I adopted that route in the first place. (It was recommended by none other than 'Cosmick' who's been a real stalwart in helping me find solutions to my new car glitches).
Bottom line is, should the 240v 16amp rated A/C DPST Momentary Push Button do the job I want it to without frying itself?
Owelly et al, muchas gracias for your patience and help.

Addendum: paulf That was my thought at the beginning of this saga. I put it to 'Cosmick' and he shot it down as a "definite no-no!"

[Edited on 27/6/12 by bobinspain]

owelly - 27/6/12 at 10:19 AM

Another thing to consider when trying to rate an AC switch for DC switching.....sorry for the non-tech language, I'm no professor:
Mechanical switches do not open instantaneously. Dielectric strength builds as the mechanical contacts of the switch open causing a short arc .
By definition, the alternating current passes 0v twice each cycle which helps to eliminate/extinguish the arc. A DC circuit doesn't pass 0volts. As a result, the arc on the contacts will be greater in a DC circuit than in an AC circuit with the same voltage and current. This can show as burnt contacts of the longer arc can cause the surrounding plastic to melt. Therefore, the stresses on the contacts will be greater for the DC circuit so the switch will have to be derated.
This could be reason why your AC switch failed. Out of interest, once replaced, why not take the switch apart and see if there's any burn marks on the contacts.

[Edited on 27/6/12 by owelly]

bobinspain - 27/6/12 at 11:23 AM

Much as I suspected owelly, A/C vs D/C.
If you check my post above your most excellent circuit diagram, you'll see my intentions re' the faulty switch.
Dr Bob.