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Conference vmszoo::rc

Title:	Welcome To The Radio Control Conference
Notice:	dir's in 11, who's who in 4, sales in 6, auctions 19
Moderator:	VMSSG::FRIEDRICHS

Created:	Tue Jan 13 1987
Last Modified:	Thu Jun 05 1997
Last Successful Update:	Fri Jun 06 1997
Number of topics:	1706
Total number of notes:	27193

1416.0. "Rx-to-servo signal encoding" by PCL::JAMES (Object Disoriented) Mon Mar 30 1992 11:27

Does anybody know how the receiver-to-servo signal is encoded these days?

An older scheme I have seen uses two brief positive-going pulses.  The time
between these pulses is proportional to desired servo position.  The servo has
has an internal timer whose delay is proportional to actual servo position.
The difference between the two intervals drives the motor correction current.

I this the standard scheme these days?  Do any radios use a single pulse,
whose length is proportional to desired servo position?  Specifically, anybody
know what comes out of a Futaba or Airtronics RX?

Thanks, Ralph.

T.R	Title	User	Personal Name	Date	Lines
1416.1	Single Pulse is todays Standard	LEDS::WATT		`Mon Mar 30 1992 13:58`	14
	The standard seheme is to use a single pulse between 1 and 2 msec in duration. Servo position is proportional to the pulse width. There is a chip in the servo that compares the pulse width to the pot position and drives the motor until the pot position matches the pulse width. Center position is 1.5msec pulse. The frame rate is about 20/second. Most modern servos are interchangable except for the connectors. They use three wires and run off of about 5 volts (4 cells). Two wires are the power and ground and the third is the pulse signal referenced to the same ground. The pulse amplitude should be about 4 volts. This amplitude varies from one receiver to another, but most servos will work over a wide range of pulse amplitudes. Charlie
1416.2	NE544	PCL::JAMES	Object Disoriented	`Fri Apr 24 1992 18:05`	14
	I'm looking for a Signetics NE544, the servo driver chip that converts the Rx output to motor current. They used to be in all our servos, but. . . Digikey says the Signetics version is discontinued. Anybody know who makes 'em now? Or, is there something different in our servos these days? Anybody got one open to see the chip manufacturer and number? Panasonic has been suggested. I know, I could open my own. . .but I've been out of R/C for a few years and won't have my new radio for a week. I want to start looking for the chip sooner. Ralph.
1416.3	Test & Calibration Gear	BAHTAT::EATON_N	Nigel Eaton	`Tue Jun 23 1992 13:51`	14
	Don't know if this helps, but here goes.... A UK magazine (RCM&E) just published plans for a test/calibration unit for radio gear. I don't really understand all this electronics stuff (software guy y'understand) but it all looks very interesting! If this article will help, let me know and I'll let you have some more details Regards Nigel Eaton
1416.4	found NE544	SHALOT::JAMES	Object Disoriented	`Wed Jul 08 1992 23:52`	11
	Thanks, but. . . I have found the NE544. Signetics sold the dies to Ideal Semiconductor in Fremont California. They sell 544's for $8 subject to a $100 minimum order (say you're a modeler or you get the $250 minimum story!) I bit the bullet and have several on hand. I will have a few left over if anyone needs one. r.