Does anyone here know anything about radio-controlling things OTHER than
models? This means knowledge of r/c itself, rather than just buying transmit
and receive black boxes from a model shop!

In particular, I'm looking to make a remotely controlled 4 or 6 channel
audio
mixer, which will have the manual slider pots in the transmitter, remote
from the mixer itself, which will in turn NOT have sound level pots moved by
motors or servos (too slow and too power hungry), but use fets or chips
controlled by
integrators or dacs from the receiver.

Can anyone suggest someone with knowledge of this sort of electronics, or
perhaps any book or publication that might help.

I know that if I had a lot of money, I could go to people like Strand
Electric and buy this off the shelf, but it is for a model engineering club,
where we have problems with the in-house sound system, which is too remote
(and uncontrollable) from our meeting.

If anyone can help - many thanks in advance for anything you can offer or
suggest.

Dave. BSMEE, Bristol

"speedy2" wrote in
:

Does anyone here know anything about radio-controlling things OTHER
than models? This means knowledge of r/c itself, rather than just
buying transmit and receive black boxes from a model shop!

Why do you want to reinvent the entire wheel? Why not use the existing
radio transmitters/receivers and just play around with the PWM signal from
each receiver channel?

In particular, I'm looking to make a remotely controlled 4 or 6
channel audio mixer, which will have the manual slider pots in the
transmitter, remote from the mixer itself, which will in turn NOT have
sound level pots moved by motors or servos (too slow and too power
hungry), but use fets or chips controlled by integrators or dacs from
the receiver.

RC servos may be power hungry, but they certainly aren't slow -- you can
buy models that will travel from end to end in a fraction of a second.

My suggestion is that you use off the shelf RC items -- they are extremely
cheap and reliable. If you dislike mechanical servos, then you should look
for the electronic speed controls (variable resistance based on the PWM
signal from that channel). Here's a link if you want to build your own:
http://www.math.niu.edu/~behr/RC/speed-ctl.html
Of course, there are dozens of these that you just buy off the shelf --
just search for "rc electronic speed controller" on google.

Can anyone suggest someone with knowledge of this sort of electronics,
or perhaps any book or publication that might help.

google knows all... :-)

"Murray Peterson" wrote in message
...
"speedy2" wrote in
:

Does anyone here know anything about radio-controlling things OTHER
than models? This means knowledge of r/c itself, rather than just
buying transmit and receive black boxes from a model shop!

Why do you want to reinvent the entire wheel? Why not use the existing
radio transmitters/receivers and just play around with the PWM signal from
each receiver channel?

In particular, I'm looking to make a remotely controlled 4 or 6
channel audio mixer, which will have the manual slider pots in the
transmitter, remote from the mixer itself, which will in turn NOT have
sound level pots moved by motors or servos (too slow and too power
hungry), but use fets or chips controlled by integrators or dacs from
the receiver.

RC servos may be power hungry, but they certainly aren't slow -- you can
buy models that will travel from end to end in a fraction of a second.

My suggestion is that you use off the shelf RC items -- they are extremely
cheap and reliable. If you dislike mechanical servos, then you should
look
for the electronic speed controls (variable resistance based on the PWM
signal from that channel). Here's a link if you want to build your own:
http://www.math.niu.edu/~behr/RC/speed-ctl.html
Of course, there are dozens of these that you just buy off the shelf --
just search for "rc electronic speed controller" on google.

Can anyone suggest someone with knowledge of this sort of electronics,
or perhaps any book or publication that might help.

google knows all... :-)

Thanks for your comments. Is it possible to get r/c transmitters that have
normal rotary or slider pots - not the paddle type of things which are the
only sort I've seen. I want a control that is just like a normal sound mixer
, with pots that go from zero to max, and not centre zero types, except that
it will be remote from the actual mixing "works". I/R is not an option,
because of both distance and of the signal getting blocked by a moving
lecturer(!), nor is X10, for lack of nearby power sockets.

I've contacted model r/c suppliers, but they have nothing suitable.

I have now earned that Analog Devices make a very good 6-channel mixer chip,
that it can be controlled by a 3 or 4 wire serial connection from a pc. They
supply software for this. I have wondered whether this serial link can be
replaced by a radio link, since there are no return signals along the link
from the mixer chip, and perhaps use a pair of el-cheapo 49 Mhz walkie
talkies with the ptt on the transmit one hard switched. This would cut out
the need for servos and their power supplies, making the whole thing solid
state without any mechanicals being involved.

Dave.

"speedy2" wrote in
:

Thanks for your comments. Is it possible to get r/c transmitters that
have normal rotary or slider pots - not the paddle type of things
which are the only sort I've seen. I want a control that is just like
a normal sound mixer , with pots that go from zero to max, and not
centre zero types, except that it will be remote from the actual
mixing "works".

If you were considering building RF equipment from scratch, then it will be
child's play to disassemble an existing transmitter, measure the pot's
resistance range, and replace the self-centering pots with ones of your
choice. You can put the whole shebang into some nice box that even looks
like a mixer...

I have now earned that Analog Devices make a very good 6-channel mixer
chip, that it can be controlled by a 3 or 4 wire serial connection
from a pc. They supply software for this. I have wondered whether this
serial link can be replaced by a radio link, since there are no return
signals along the link from the mixer chip, and perhaps use a pair of
el-cheapo 49 Mhz walkie talkies with the ptt on the transmit one hard
switched. This would cut out the need for servos and their power
supplies, making the whole thing solid state without any mechanicals
being involved.

You still seem to be confusing the existing R/C equipment with required
usage of servos. Split up the problem as follows:

1. Purchase existing r/c transmitter and receiver (note -- NOT servos)
2. Modify existing r/c transmitter to use pots/sliders of your choice
3. Add whatever circuitry you desire at the output of the receiver.

Step #3 requires that you be able to read a PWM (pulse width modified)
signal from each channel and convert that signal into whatever electronic
mechanism that you desire. There is no requirement that you use
mechanical servos -- the circuit can be used to control an electronic "pot"
of your own manufacture. I even provided a link to some circuits that do
exactly that.

There is no need for you to build any RF equipment -- just use an existing
(and cheap) transmitter and receiver. At no point do you need to buy, use,
or modify a mechanical servo; they are nothing but one type of device that
uses the PWM signal coming out of the receiver channel.

Attempting to use walkie-talkie circuitry to send/receive your signals is
going to cause you an amazing amount of grief. Why not just use a
transmitter and receiver that is already designed and built to do exactly
what you want?