Lighspeed Plasma III Complication

Here is an unexpected complication with the design of the Plasma units that I wanted to see how others are dealing with.

The 15 pin D-Sub "Input Connector" has the expected wiring to connect the crankshaft sensor to the ignition box as expected...plus...the same 15 pin D-Sub connector has four more wires in the connector (the power and ground for the unit and the tach output wire and the tach ground wire).

The instructions say that you are supposed to run the power wire directly from the ignition switch to the unit and the ground directly from the battery NEG post and not have any splices in between.

This is all great until you need to remove the engine and then you discover that you are stuck with only two options"

-1 You have to remove the prop and flywheel to get access to the crankshaft pickup PC board and then unbolt it and hang the delicate PC board from the wires on the firewall while you are doing your engine work...OR...if you dont like that option...

-2 You have to unwire the power wire at the ignition switch and the ground wire at the battery NEG post and pull them through the airplane...and you also have to cut the tach and ground wires (or unwire them from their terminal ends.

So has anyone else dealt with this issue?

I wish the design had one connector dedicated for the crankshaft sensor wires and a second connector to handle the power/ground/tach/tach ground wires so when ti comes time to pull the engine just unplug the one connector and pull it through the firewall conduit.

Without that "Wish List Feature"...the question is...What do you do when you need to do some engine work?

Did you splice some kind of 4 pin connector for the power/ground/tach/tach ground wires so you can disconnect the airplane from the 15 pin D-Sub and then pull the 15 pin connector through the firewall and hang that from the engine while you are removing the engine?

Any thought or ideas would be appreciated!!!

Try a pin puller.

https://www.steinair.com/product/insertionremoval-tool-for-standard-d-sub-pins-mil-spec/

breister said:

Try a pin puller.

https://www.steinair.com/product/insertionremoval-tool-for-standard-d-sub-pins-mil-spec/

Click to expand...

Lightspeed uses soldered D-sub connectors, so no pins that can be pulled. I used a D38999-style mil-spec round connector at the firewall for the crankshaft sensor wiring. If they're good enough for military aircraft, they're good enough for RV's. Only caveat is that you have the proper crimpers to do a good job crimping the pins.

Is this a right now kinda thing or a in case I ever have to? When and if it comes up, I'd snip the wire at the brain box connector and plan on replacing with crimped pin d-sub or snip and splice near the firewall. In fact, I used crimped d-sub connectors and didn't use the provided soldered ones.

Klaus is concerned that people will make poor wiring decisions, adversely affecting reliability. Valid concern, but... For one thing, his wiring scheme makes no mention of any sort of circuit protection device at or near the battery to protect the wiring, just a pullable breaker, probably at the panel, and a possible switch. The breaker is there, as near as I can tell, because he's got a crowbar in the ignition unit for overvoltage, not primarily for wire protection. I ran robust fusible links directly from two batteries spliced to AWG 20 wires to the breakers and then to the switches for each of two ignitions. Grounds I ran to the forest of tabs just like everything else. No ignition noise observed.

Ed Holyoke

>is this a right now kinda thing or a in case I ever have to?

Already done this morning

>When and if it comes up, I'd snip the wire at the brain box connector and plan on replacing with crimped pin d-sub or snip and splice near the firewall. In fact, I used crimped d-sub connectors and didn't use the provided soldered ones.

It just came up...I snipped the wires and will crimp the Sub-D on again. What I decided to do was to have a Sub-D in the four wire ship bundle and then I can undo that connector and remove the connector from the box and slide both out through my firewall hole.

>his wiring scheme makes no mention of any sort of circuit protection device at or near the battery to protect the wiring...I ran robust fusible links directly from two batteries spliced to AWG 20 wires to the breakers and then to the switches for each of two ignitions.

Good idea!!! Yes my wire from the battery terminal to the circuit breaker on the panel is always hot with no protection...Where did you get the fuseable link?

>Grounds I ran to the forest of tabs just like everything else. No ignition noise observed.

I felt more comfortable with the ground at the battery terminal

THANKS AGAIN

When I installed my dual plasma iii I ran the presoldered connector through a large conduit through the firewall. I had a problem with the crank sensor board and upgraded to the mini sensors. I couldn?t reuse the wiring already ran and couldn?t fit the new connectors through the now full conduit so was forced to cut the new 15 pin connectors off and resoldered the wiring to the connectors. It?s a delicate operation but if you have soldering skills isn?t too bad. Another option is crimp connectors but I am more comfortable with soldered connections for this application.

Rolled my own fusible links per AeroElectric Connection. It occurs to me that I never really tested the breaker to make sure it blows before the link. Might be a worthwhile test. Maybe I'll do it at annual.

Ed Holyoke