Solid Snake

What type of signal goes from the radio reciever to the ESC? Is it analog, PCM or something else?

flatfour

My Feedback: (8)

The exact same signal that goes to a servo.

I would call it an analog signal. It pulses about 50 times a second.
The pulse width (duration) varies between 1 - 2 milliseconds depending on the position of the sticks. When the pulse is 1.5 ms, that is considered "center"

I'll try and get a picture from the scope.

flatfour

My Feedback: (8)

This is from a 9C and 148DF receiver operating in PPM mode.
The scope is hooked to the aileron channel of the receiver.
This is a "train" of the pulses. Each pulse peak is right at 3 volts.
This is with a 4.8V pack

Solid Snake

So wouldn't it be more of a PCM signal since it depends on pulse width? So it's a pulse that varies from 1-2ms that occurs every 20ms right? Is the output around battery pack voltage?

flatfour

My Feedback: (8)

Here is a "zoom" on just one of the pulses. Stick is in the center position.

flatfour

My Feedback: (8)

Here is the stick at full left. This is with the "default" radio settings. If I crank the D/R to 140%, the pulse goes to around 0.92 ms

flatfour

My Feedback: (8)

Last one, stick at full right. Again, if I crank D/R to 140%, pulse goes to 2.12ms

flatfour

My Feedback: (8)

No, PCM takes the stick position and converts it to a number from 0 to 1024. That number is sent to the receiver, and the receiver turns it into one of the pulses shown here.

Some good reading can be found here.

http://www.wtp.net/DBEST/Sup7388tips.html

Solid Snake

So what are the minimum and maximum pulse widths? Do car and truck radios also use the same scheme? What about the throttle control?

flatfour

My Feedback: (8)

Ground (car) radios are exactly the same. The minimum and maximum depend on your radio and what settings is has.

You can make a simple circuit with a 555 timer to "simulate" a radio.

http://www.uoguelph.ca/~antoon/gadgets/servo3.htm

LoboFlyer

The official type of signal sent to the servo is PWM (Pulse Width Modulation). The speed controller takes this servo pulse and converts it to a higher-current signal at a different frequency (appropriate for a DC motor).

Nice scope pics, flatfour!

HarryC

My Feedback: (1)

The different manufacturers don't use the same absolute standard. Either side of neutral with travels set to 100%, JR uses 0.4ms whereas Futaba uses 0.43ms. So a JR signal varies from 1.1 to 1.9ms, Futaba varies from 1.07 to 1.93ms. Multiplex uses 0.55ms, if recentred to 1.5ms this gives travel of 0.95 to 2.05ms.

They all use different maximum % travel, JR allows 150%, Futaba allows 140% and Multiplex 109%. Multiply the times by the % and lo and behold they all come to a maximum of 0.6ms either side of centre. 0.4*1.5, 0.43*1.4 and 0.55*1.09

So all brands allow a max of 0.6ms either side of centre, the difference is where within that range of 0 - 0.6 they define the 100% point.

Harry