Switches for ignition

[SP1]

Hi All,
I'm a little confused by the ignition schematics. Both the magnetron and secondary shows switches that should be normally open. I believe that means the switch are spring loaded and will revert to the open state if we're not holding the switch down.

Don't we won't switches that will stay in the position we set them in (no spring loaded)? Open for the magentron and closed for the secondary (for the engine to run)

Would someone be willing to list part numbers for the switches they used?

Thanks

[OneTallShort]

You are confusing NO switches with momentary (MOM) (MT) switches. One refers to the contacts, and the other is the switching position. SPDT (Single pole, double throw) or DPDT (Double Pole, double throw) is what you want...DT referring to "Double Throw" rather than MT (momentary thrown)

Momentary switches (momentary throw) are oftentimes called out as OFF-(ON), where a held (thrown) position switch is OFF-ON. With 3 position switches you can find OFF-ON-(ON), ON-OFF-ON, (ON)-OFF-ON, (ON)-OFF-(ON) etc... Three position switches almost always have three terminals per pole. Two position switches can have either two terminals or three terminals (a NO and NC side) depending on use.

Poles are the number of contacts that you break. Most typical are the Single pole and Double pole varieties.

See this article for everything you always wanted to know about switches...
https://bandc.com/wp-content/uploads/20 ... atings.pdf

Here is a link to the single pole variety.
https://bandc.com/product/toggle-switch-single-pole/
You'd want the S700-1-2 (or -3) for the electronic ignition. (the -2 has two terminals, the -3 has 3 terminals, either would work)

It depends on how you want the Magnetrons wired...on two switches or just one switch. If just one switch, then you'd need a double pole switch. With the mag switches you are wiring them to be grounded (switch in conducting position) when "Off" which means mounting a -2 upside down (for off being down), or use a -3 with the correct terminals connected to ground.

B & C has just about every variety of switch contact and throw option available...

Hope this helps!

Gregg Short
N715SX (Still under construction)
Burbank, OH

[sonex1374]

Sam,

The wiring diagram for the AeroVee is not trying to indicate spring loaded switches - just regular toggle switches. The mag switch "grounds-out" the magnatron ignition, meaning that when the switch is "closed" the connection is made and the mag is off (grounded and thus won't spark). The electronic ignition is powered by the battery so when the switch is "closed" power can flow to the coils and the ignition is on.

Typical graphics used in electrical system diagrams are below. There is some variation in how these are shown, however.

"Normal" toggle switch

Toggle.png (3.06 KiB) Viewed 1338 times

Push Button switch

Push_Button.png (4.5 KiB) Viewed 1338 times

Momentary (Spring-loaded) switch

Momentary.png (4.16 KiB) Viewed 1338 times

Jeff

[Rynoth]

SPDT (Single pole, double throw) or DPDT (Double Pole, double throw) is what you want...

Gregg, good explanation post but I'm questioning this part? I don't see a need for double-throw switches for ignition.

A SPST (single-pole single-throw ON-OFF) for secondary ignition (if only 1 wire being used to power the secondary ignition), otherwise DPST (single-pole single throw ON-OFF) for primary ignition (mounted upside-down) or secondary ignition if 2 wires present, would seem to be what's needed.

[n502pd]

All good info and very correct. I wish to add that the rating on any switch used for DC...battery operted things, should have a DC ratinbg printed on their side. AC rated switched will work on DC circuits for a while, but will eventually fail by either not making connection, or being unable to brake the connection, due to contact sizing and spacing when opening caused be the large opening dc arc on AC switches, burnning up the contacts, compaired to DC switches. Using an AC rating of120/250vac, at 10 amp and a dc rating of 28vdc at 10 amp would be very acceptable. not all switches have the dual ratings, so look closely. if no ratings on the switch, use it for a toy elswhere else!

[OneTallShort]

Ryan,

The -3 switches only have two positions "On" and "Off", but there are 3 contacts in the back (per pole). That means that the center wire connection will flip between the two outside connections (typical, but verify on your switch). That means that you can mount the switch right side up, and still use the up switch position as a broken contact for the mags. It's a minor thing, but the switch orientation key is visible on the face, so the upside down is slightly noticeable, and the -3 are the same price as the -2...

I'd suggest using a double pole switch for the mags, as that keeps them more independent and less likely to cause noise. You can also use 3 single pole switches (one for each mag, and the electronic ignition), but I decided that was overkill. YMMV.

Hope that makes further sense!

Gregg Short

[SP1]

Thanks very much all for the information. It was definitely the normally open part that was confusing me.