Tachometer/RPM

[badia358]

I have a Lasar Electronic ignition installed in my RV-6A project. I have not installed the engine eyt, but want to make sure that I am wiring the EMS-220 correctly. I currently have the Right and Left p-leads conneted the EMS D37 connector pins 32 and 33 through a 30K ohm resistor. I noticed in the Laser manual that they provide a wire (brown) for engine RPM.

Does anyone know if the way that I currently have it connected with p-leads through 30K ohm resistor is correct or should I be connecting the Laser RPM brown wire output to a different pin of the EMS D37?

 

[schristo]

The resistors are intended to knock down very high voltage that is coming from the P-leads off of the magnetos... typical electronic ignitions send a managed voltage pulse of 5, 10, or 12 volts that can connect directly to the 220 inputs.  For RPM dynon gives two options for pickup, low voltage (under 10) and higher.  The laser system sends either a 5 or 10 volt signal and should likely be on the low voltage 220 RPM inputs.  You will also need to set pulses per revolution with the Dynon unit... likely 2 pulses/rev

 

[badia358]

Thank you. Connected directly (no resistors) to the low voltage pins 34 (Left RPM) and 35 (Right RPM) of the EMS D37 connector.

 

[mmarien]

On the E-Mags there is a 12V tach signal in addition to the P-Leads. I just connected it to the regular EMS pins 32/33 without the resistor. Since each E-Mag puts out the signal you can connect each one to a EMS pin, but the signal is available even when the P-Lead is grounded. EMS pins 34/35 are for low voltage (2V-10V).

 

[badia358]

Thank you. Great to have options.

 

[starkw1]

I know there has been a lot of discussion on RPM inputs and tachometer transducers in the EMS sections of this forum, but I am still not clear on the best setup for SkyView for my situation which includes a Lycoming IO-360, one Slick magneto, and one LightSpeed Plasma II system. 

The SkyView manual address both magneto and electronic ignition RPM sensing, but does not seem to address the situation where you have one of each.

If you have one mag and one Plasma II, does one connect the mag P lead to one of the Standard RPM inputs, and the Plasma II to one of the Low Voltage RPM inputs?   If so, what does the system actually display when either ignition system alone is ON, or when both are ON?

Overall, is it preferrable to use a separate single RPM transducer such as the UMA or Garmin hall effect transducer connected to a standard RPM input?

If this has already been addressed on the forum and I missed it, please point me in the right direction.

Are there other options I should be aware of?

Thanks for the follow up


Warren

 

[skysailor]

I have the same setup as you do Warren. Your connection strategy is correct. The Skyview will show the RPM using the ignition system still operating as you secure each during a pre takeoff check. This will happen seamlessly to you. If one signal becomes invalid (you just turned it off) the other is used to provide your RPM. When both are operating as is normally the case in flight, both signals are the same. Dynon support can probably tell you which the EMS uses in this case but it should not matter.

 

[Edwardoc]

I too have the LASAR system installed and I connected the Brown wire to Pin 34(low voltage input) on the EMS with a 22K / 5 Watt resistor installed in series.  I believe I set the Software for 2 pulses/revolution but I would have to confirm that.  If it doesn't read correctly, you just change the Pulses/Rev until it does read correct.  Without the resistor RPMs read OK at idle but at 1800 RPM, the RPM would peg at 3000 as there was not enough time for the voltage to drop betweed peaks.  22K works great.  Very stable readings.   

 

[dynonsupport]

Hook one to the left, one to the right. Use either the high or low voltage pins as appropriate for the individual input, and, you can mix and match (ie, one left= high voltage, right = low voltage, and there's no additional setup to do if you do this). Make sure the pulses/rev are set correctly for each input.

The system is always monitoring both, behind the scenes, but only displays one at any given moment. You don't know (or care) which that is, because they'll be the same, as long as you've gotten your pulse/revolution settings right. During a mag/ignition check, if RPM goes to zero, but the engine's still running, you know that you have a problem with that side's signal path.