Connecting a YGE ESC to the CGY750

[Steve Evans]

I made a resistive divider to drop the 5V output from the YGE-120LV tacho output down to the 3V required by the CGY750. I used a 2K7 and 3K9 resistor which seemed like it should be OK as I'd measured the current required for the CGY750 to see a high (97%) input as only 12uA.

With my logger hooked up I was surprised to see how noisy the tacho signal was as shown below.



I then went back to my divide by 4 pre-scaler, details HERE, and got a much cleaner signal.



Pity the connectivity isn't simpler. Smaller value resistors should provide a cleaner signal. Some more experimentation is required, but for now I'll try to get it set up using the pre-scaler.

Yet to take to the air with 1.3, so keen to try that!

Steve

[Matwes]

Subbed..

I'm about to install the same setup in my T-Rex 550 but with the YGE 90LV.
A forum member at our local heliforum has done this installation in his heli.

The slave cable is splitted and the orange signal is plugged into the speed sensor port on the VBar, the +/- in one of the free servo ports on the main unit.

Could this be a working setup on the CGY750 as well?

[Steve Evans]

The CGY750 1.3 update doc clearly states "Note: The input signal range of the CGY750 is 0.0v-3.0v. Exceeding this voltage range may cause damage to the CGY750".

I'll contact YGE and see what they have to say about dropping the output level. If they are using an open collector output then a simple pulldown of the correct value may give a clean signal.

Steve

[davebnz]

Hi Steve,

Did you hear from YGE on this ? I too would love to see the YGE work with the CGY 750 in GOV mode via the YGE programming cable.

Thanks

David

[Steve Evans]

Do NOT connect a YGE ESC directly to your CGY750 Rsen port.

See below why.

I received the following reply to a query from YGE.

You can use the phase sensor as Millstioe from helifreak forum. The 3V input from CGY750 will not goes damage becausece we use 470 ohms in series to the output. No pull up or pull down directely from the processor port full bridge source/sink 20/20mA max.
The difference of the current between 3 -> 5V with 470 ohms is 4.25 mA maximum. With this small current, you can not destroy anything. For safety, you can but again 470 ohms in series.

Btw. the Mikado Vbar is also 3.3V input.

I replied.

I am concerned that 4.25mA might cause a problem; I'd really rather not have that flowing through whatever clamp diode the input has and injecting noise onto the CGY750's internal supply rail.

If I were to add a 680R resistor as a pull down, this would give me 2.96V max voltage with a load of 4.3mA on the output. I measured the input current into the CGY750's Rsen input, connecting an ammeter between +3V and the input, and read only 12uA, so that wouldn't upset the voltage set by any such resistor network.

Would you recommend that as a simple way to get a clean 3V output?

Do you have a 470R resistor in series with the output on all your ESCs?

To which YGE responded.

Thats a good solution with 680 R as a pull down resistor.

On all our esc's with Vbar output is a 470R Resistor in series.

And.

Of course you can publishing the solution on helifreak forum or other platforms.

I then responded.

Today I made up a lead with a 680R pulldown between the signal and ground and fitted it to my Align Trex 500 ESP. The CGY750 reported the current RPM as hoped, but I noticed that the Rsen signal input level was being reported as having a 99% peak, which is higher than the normal maximum of 96%. I therefore measured the voltage being fed into the Rsen input of the CGY750 and was alarmed to find that it was over 4V! I immediately powered off, and disconnected the lead from the Rsen input. I then reapplied power, and was relieved to see that the CGY750 was still working. The YGE was driving 4.12V into the 680R load. This is more that one would expect if there was a 470R resistor in series with the output as you state below! Indeed as only 0.88V appeared to be dropped across the output drive resistor I calculate the series resistance to be only 145R.

I'm feeling fortunate not to have destroyed my CGY750!

Of course I could add a 330R resistor in series with the output, but I thought you'd like to know.

I got no reply.

Steve

[ilyxa]

Any infos about HV ESC (120HV in case)?

[Steve Evans]

No, but I suggest you stick a voltmeter on the output.

Steve

[ilyxa]

I'll do it soon, good (and simple ) idea.

[ilyxa]

Ok, few changes (for me), seems like picture is enough for understanding. Voltmeter is not our way

Blue: HobbyWing sensor, G(black) - S(white) - V(red). G+V = straight 3.3V (LDO on board of CGY750).



In common: 1 RPM = 1 Hz. Very simple, KISS rule in work

Blue: HobbyWing Sensor, voltage 3.3V (powered from CGY750 unit, small LDO, current less than 100 mA).

Yellow: YGE 120HV, voltage 5V (powered internally, seems important, Vamp is not voltage from BEC as I expected), pull-down resistor seems enough. Pin - Brown=Ground, Red=Signal, Yellow=i-have-no-idea-what-is-it, frequency is about 72 Hz, not changes with RPM, voltage or any else, very stable, this wire always shorted on ground in my setup:



more info (fun with generator soon to come (in my blog 1st .