Oil Pressure Sensor & Dynon/Hobbs

I'm installing a Dynon FD-180 but I also wanted to put a Hobbs meter in the panel. The Dynon comes with an oil pressure sensor. The Hobbs also came with an oil pressure switch/sensor.

I hate to hate to install two oil pressure sensors because of extra weight and another hose that can potentially leak.

Anyone figured how to run the Dynon and the Hobbs off a single sensor?

... Bill

Hi Bill,

Don't think you can do it. The Dynon sensor unit puts out a voltage proportional to the pressure while the Hobbs just wants a contact closure at some set pressure. As you said, the Dynon unit is a sensor while the HOBBS unit is a switch. The Dynon will give you a hobbs time which starts counting at a preset (~15 psig) pressure. So why do you wish to have a seperate hobbs counter? If your after saving weight just use the Dynon. If you really want to use a seperate Hobbs, the Van's manifold block should have an extra port on it to mount the Hobbs switch. No extra hoses needed.

IMHO

Bill

BillC said:

So why do you wish to have a seperate hobbs counter? If your after saving weight just use the Dynon. Bill

Click to expand...

Bill, you're absolutely right. But I didn't realize this until after I cut a hole in my panel for the Hobbs, and don't really want to have it on the panel and not working. I might see if I can fill the hole with something else. Maybe put the passenger warning placard over it.

... Bill

I am going to use the Hobbs on the Dynon and a separate mechanical Hobbs mounted in the panel.
I just like being able to look over and record the time off of a mechanical counter after I have shut down (just a creature of habit I guess).

I mounted the Dynon sender and a pressure switch to the standard Van's manifold that is available from their on line store. There is no need for an extra hose.

Hope that this helps.
Jeff

Bill,

Please see my installation below, the oil pressure switch is in the top location of the sensor manifold and just below it is the Dynon oil pressure sensor. The two are joined with some 1/8" copper tubing. Using the oil pressure switch not only allows you to use a separate Hobbs meter but also an idiot panel light indicating you oil pressure is below 5lbs (I think) and your ignition is on.

Hey Joe,

I've got a Dynon D-180 and a mechanical Hobbs as well. I was planning on mounting mine the same way (actually doing it tonight). Another advantage of the mechancial hobbs is if you ever crash the memory in the Dynon you have the meter. It can happen and don't let anyone tell you other wise. Have you ever updated the software in the D-180 yet? If it fails in mid-stream you could be in real trouble as in sending it back to the factory for a reset. The applet from Dyon actually warns you of this prior to running the routine. No guarantee the hobbs time would come back correct. (Maybe the Dynon guys could chime in here and correct me if need be?) I'm an I.T. guy, I see this thing from time to time. Any problem with using 1/8 ID aluminum tube for the jumper instead of copper? I think it's rated high enough for Oil pressure.

You don't need any jumper. Just screw the Hobbs pressure switch into the side manifold hole instead of the jumper. Make a .125 spacer for between the manifold and firewall. Done.

Larry

Place witty title here...

Already thought of that. A .125 spacer is cutting it a little close. The sensor will probably rattle against the firewall if done that way due to vibration. I considered going a bit bigger with the spacer, probably can without destablizing the manifold too much. The jumper is still a good option. 2 AN816's with collars and nut couplings and you're there.

Mulling it over....

I'm thinking I can mount both oil sensors (dynon and hobbs) on the VA-168 with an AN 915 45 degree elbow. Any good reason to pay extra for brass over aluminum?

I also like the mechanical Hobbs and used a spacer to allow me to mount both on the block with no jumper. No issues so far (420 hrs). I do like the ability to look at the meter after I have shut down. If only the numbers were a bit larger and easier to see....

You can always manually reset the Hobbs on the Dynon if you're keeping track. I typically use one of the columns in my logbook to record the manual Hobbs after each flight, so I suppose one could do similarly by looking at the Dynon at the end of each flight. Alternatively, if you note the Dynon Hobbs reading occasionally in your logbook, you could always back out the current reading from the hours flown (assuming you are the only pilot).

cheers,
greg