Replacing Switches (Caution! Nerdy)

[MEXICOWANDERER]

Not satisfied with being hip-deep in projects I am looking into replacing the lamp and water-pump switches in Quicksilver with membrane touch switches. They glow orange with about 1.5 ma current, and have touch buttons. Totally environmentally sealed.

But I need to fire NPN MOSFETS (TO247) and have been searching for something that does not live up to the moniker FET (Fire Emitting Transistor)

I ran across this possibility...

http://www.infineon.com/cms/en/product/power/power-mosfet/20v-650v-automotive-mosfet/20v-40v-n-chann...

Membrane slid-state switches would certainly eliminate issues with depth of switch body.

Rockers are not reliable and toggle switches are oogly.

The idea of running power directly to the lamp with only a micro breadboard and TO247 heatsink appeals to me. Micro-cable can connect the membrane switch.

[GordonThree]

Your beast mosfet will switch plenty of amps with 5v input.

I think happycamper is suggesting the use of modules intended to work with an arduino, not an arduino processor itself.

Do your lamp fixtures have independent grounds, for the n-fet to switch?

Toggle capacitive switch
http://www.dx.com/p/digital-capacitive-touch-sensor-switch-module-for-arduino-toggle-mode-blue-black...

[MEXICOWANDERER]

To clarify:

The vehicle is 24 volt. The lamps are a pair of series 12-volt each a total of twelve doubles. If I am not mistaken Arduino is a 5 volt control?

[happycamper002]

Have you looked into Arduino Kits?

Since you require a none-too-conspicuous, oogly unreliable rockers and toggles (I don't like them either.) Arduino kits may have what you need.

They have the matrix array that you can glue onto any flat surface. This is similar to those fold up keyboards that you can wash in the sink. . . and very thin. But since you only need to control two appliances, the number of buttons would be too many. With 16 keys on it and you would only need two, you would have 14 unneeded buttons. Cat. Arduino AVR

The other option is: the touch capacitive discharge sensor module model TTP223B. No flip switches, or buttons and toggles. Just touch it and off you go. The good thing about this is you can run this off the 12v power (although you can also use a battery.) The sensitivity is also adjustable. This is similar to those Delta faucets that you just touch to open the tap. You would need two. . . one for each appliance.

Either of the above would require the relay to handle the high current like pumps etc. You can mount this relay right next to the appliance being controlled. For the two appliances you would need the 2-channel. Cat. AVR DSP.

Another plus: these are shipped from here in US so you won't have to wait 3 weeks for the shipment from China. Although they are made in China. (LOL) There are several Arduino outlets here in the US.

Check them out. For that project you have in mind, $30.00 would be more than what you need to cover it. Most of these can be found on Ebay or Amazon.

Good Luck.

[GordonThree]

MEXICOWANDERER wrote:

The clicky no workee. Asks if I want to bookmark it.

Looks like I typo'd an extra space into the clicky. It should be working now.

[MEXICOWANDERER]

That's me. Beast

The membrane switch is about 1/4 deep and has sort of an un-earthly orange glow. Good for 30ma@ 5 volts. The membrane is 5mm which is plenty thick to resist wear-through. I would imagine non ammonia window cleaner to remove smudges.

I like the idea of fishing a jacketed stranded 24-gauge pair from the circuit board (adjacent to the lamp overhead).

Yes, a latching circuit is called for. And thank you for the recommendation.

The water pump circuit is going to need a serious flyback network and this is where those 17 volt ultra-fast (2ns) TVS are going to earn their pay. I purchased some 1-watt 1-Kohm resistors for load-side pull downs.

I am working with 24 volts so entry into the lamp means dealing with a voltage regulator circuit or leaving them as is - 2 12-volt lamps connected in series.

All because I stumbled across a "deal": 33 membrane switches, with stainless steel fascia for $20.00 (haggled) and seven fifty to ship from Mass. I suspect the gizmos are military surplus.


The clicky now workee. I bookmarked it.

[GordonThree]

Pd of 380 watts and pulsed Id over 1500 amps, that is a beastly mosfet! Continuous Id of 180 amps, limited by the plastic package. That thing could probably switch a good sized dc motor, or work as a battery isolator / selector.

For switching water pumps, lights or just about any other DC load you could find in an RV, I like these cheap transistors...
50v, 21a N-Fet

[GordonThree]

The new switches you want to use are cool looking, but don't handle much current??? So that's why you're looking at using a mosfet?

You'll want a latching flip-flop switch to drive the mosfet. One input pulse turns it on, and it stays on until another input pulse turns it off.

something like this item on the mighty e-bay:
clicky

On board 5 amp mosfet for small loads, or use it to toggle a relay or larger mosfet for big loads.

I'll read up on the mosfet you selected. What your expected max load? Water pump is inductive and mine did not like being switched by a mosfet, I suspect the turn on time is too fast. It was causing a large inrush current spike and causing other items on the dc bus to freak out.