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From: quartlow@netcom.com (Len Turnbow)
Subject: Re: radio control of parts
Message-ID: <quartlowCt0oqw.B70@netcom.com>
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Date: Sat, 16 Jul 1994 05:04:07 GMT
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Christopher J Burian (cburian@ux4.cso.uiuc.edu) wrote:
: quartlow@netcom.com (Len Turnbow) writes:

: ]Now, if you level-shifted the outputs of the receiver to TTL levels, you
: ]could input them to a microcontroller.

: I've already done this.  All it takes is a 5k series resistor and a 4.7V
: zener to ground on the microcontroller input line, from the white wire
: of the receiver-to-servo cable.  Using 16-bit timers you can easily get
: better than 1% resolution.  But I don't have 1% fingers to control the
: transmitter! so it's more than enough to divide down the proportional
: signal to one byte-size for most applications.  

(Digital Multiplexing hack deleted)

: ]Disadvantages:
: ]  *  Your code would have to leave the E-pot settings as they were when
: ]     a "switch" signal is being sensed.

: Depending on how fast the digital circuits have to respond... You could
: debounce the switches in the transmitter and have them act as toggles, so
: each time a switch is pressed, or released, it uses a one-shot to send a 
: short (1/20 sec guarantees two samples being taken) pulse at the extreme
: end of the band.  When the receiving microcontroller sees the pulse, it
: freezes the analog out and toggles the digital.  Then it waits until it sees
: in-band analog again, then the next extreme-end occurrence will toggle the
: digital output off again.

Yup, that's the ticket.  I expect that analog transmission gates could be
used as the pass element to the transmitter.  That way, you could place each
digital signal individually.  Your one-shot could be used to selectively
enable one transmission gate per digital command.  You could assign some 
digital "switches" as toggle, others as momentary.  (If they were *all*
momentary, your 1% resolution would buy you 24 digital channels, including
generous deadband space!)

Pardon the ASCII that follows.  D^>


                       Power, probably
		/---------------O-----------\
		|		|           |           |
		\		|	    |		|
Your	--->    /  	 	|    "SW"1  \____	|
R1 of 4		\     ----	|     ____	 |______"__
		|    |    |     \    |	  |	|          |
Existing -->   [ ]<--|TG1 |-\	/<---|TG2 |--O--|   R/C    |
Pot		|    |    | |	\    |	  |  |  | Transmit.|
		\     ----  |   |     ----   |  |          |
Your   --->	/	    \---+------------/   ----------
R2 of 4		\		|		     |	
		|_______________O____________________/
                     Ground, probably.

(Snip)

: You can get that range back by soldering resistors 
: on either side of the pots.

Gotcha, chief.  Like the above?

: Chris Burian

Thanks for the feedback, Chris!                 --Len (quartlow@netcom.com)

