WTS, 235/320/360/Legacy Hydraulic Pump Controller

[Chris Zavatson]

What began as a curiosity during a phone conversation with Louis Gabriel turned into a year-long collaborative design project. Some 6 months ago we produced the first flying copy of a solid state replacement for the solenoids that control the landing gear hydraulic pump. We thought we were done, but soon realized the Legacy community had an interest in the same sort of upgrade. Subsequently the switching capacity was doubled so that both the 235/320/360 and Legacy pumps could use the same controller.

Controlling the gear is a rather critical function. Not just from a reliability stand point, but also from the perspective of avoiding inadvertent activation. Safeguards were built in as a result.

The controller is a drop-in replacement, in that all the electrical connections that feed into and out of the solenoids are identical. Key differences difference is that the solid state controller requires much less current for switching. The intermittent solenoids require 2-3A and this limits the options with respect to pressure switches. Now any solid state pressure transducers can be used.

While the individual components on the board are not really being stressed, we still wanted to test well beyond the operational requirements. This included 10,000 cycles running for two weeks straight at higher current levels and longer cycle times than will be seen in use. Continuous on-times were also tested to simulate a failed pressure switch and run-away pump not noticed by the pilot.

RF picked up by all the up/down command lines is suppressed and grounded on the board. Trigger levels are set very high so that operating in a noisy RF environment will not affect operation. We even radiated 5W at a range of 1 inch just to be sure.

The typical switch bounce that comes off solenoids, and really any other mechanical switch, was eliminated by building in a 20ms delay at the input. This means the pump starts up only once instead of quick succession of start-stop-start-stop-start.

Another benefit is reduced weight. I lost 1.25 lb when I swapped solenoids for the controller.

Controllers are available for $295 (includes shipping)
If interested, contact Louis Gabriel or myself.

[Paul Miller]

Send me one Chris, I will be putting the Legacy up for a while with the new panel so I have the jacks and can do the install and testing in June and July. I can do the paypal and give you the FL address in the payment info. I have had no problems with gear but I like the concept and appreciate the effort and testing.

[Blair Sims]

Add one for me too!

[John Cooper]

That's some very nice work there! I'll put one of those on my Christmas wish list.

[Mark Davis]

Chris,

I'm interested. My Legacy is a 28V system - any issue here?

Mark Davis

[Paul Miller]

I am 28v also in the Legacy. Chris said they can accept Paypal also.

[Chris Zavatson]

Chris,

I'm interested. My Legacy is a 28V system - any issue here?

Mark Davis

Mark,
No problem with 28V systems. In fact the 28V motor draws much less current. The most stressing combination is a 12V high speed pump.

[John Cooper]

Chris-- Does the board have the snubbing diodes on the motor leads?

[Chris Zavatson]

Chris-- Does the board have the snubbing diodes on the motor leads?

It sure does. A very large one in fact.
BTW, the back EMF current on these motors ranges from about 10 to 60A depending on the load at the time power is pulled.

[John Cooper]

... the back EMF current on these motors ranges from about 10 to 60A depending on the load at the time power is pulled.

I guess I'd better upgrade my 1N4001s then, shouldn't I.