D
Don Bruder
- Jan 1, 1970
- 0
So I've gotten my stepper-driver working as planned - four inputs,
controlling four phases of a stepper - Input goes to logic low, the
corresponding stepper phase goes "hot", while the other three phases
either stay, or go, as needed, "cold". That's good.
I've also got my sequencer working - Oscillator oscillates, feeds
counter's clock pin, counter counts either up or down according to the
state of the direction pin and enables, output of counter feeds a 1-of-4
decoder, decoder connects to the four inputs of the driver, and
everything works - Pull the counter's direction and enable pins to low,
and watch the stepper step clockwise. Pull the direction pin high and
the enables low, and watch it step counterclockwise. Pull the enables
high, and watch the stepper hold position - Exactly as planned. Yay! I
love it when a plan comes together!
Now, I want to make controlling it wireless...
I've got an el-cheapo ($6 on sale at RatShack) R/C car controller with 6
"functions" - forward, reverse, left, right, transform, and untransform.
It drives three small PM motors (set up to drive two of them together -
one clockwise, and the other counterclockwise for forward, vice-versa
for reverse, both clockwise for left, and both counterclockwise for
right, plus a third that gets driven clockwise/counterclockwise for the
transform/untransform function) via three separate H-bridge circuits,
one per motor.
The existing module is presently set up to run on a 3.6V NiMH
micro-pack, but after chasing down datasheets, I find that all the
"active" components on the board are rated to cope with maximum ratings
of anywhere from 15 to 60 volts, depending on exactly which component I
happen to be looking at. In other words, I expect I'll have no problems
with smoke leaking out of anything if I try to run it on 5, or even 12,
volts instead of the 3.6V battery pack it currently uses. In light of
that fact, I did some testing, and found that it works just peachy on
the 5 volt supply I've already got handling the sequencer/low-voltage
side of the driver (which is coupled to, but isolated from, the 12 volt
"high power" side of the board by 4n26s on each input) which should mean
I'll have two +/- 5 volt (minus any junction drop that comes into play)
outputs available from the R/C board.
As things stand, I'm planning on working with the lone
"transform/untransform" motor output as the simplest, which means I'll
have two connections - let's call them "A" and "B".
Here's what I get when I meter A and B:
No TX button pressed:
A = 0V
B = 0V
"Transform" TX button pressed:
A = +Vbat
B = -Vbat
"Untransform" TX button pressed:
A = -Vbat
B = +Vbat
Hardly surprising from an electronically switched H-bridge, huh?
I need to turn that into two independent logic outputs, "X" and "Y",
like so:
No button pressed:
Output X: Irrelevant (to be used as counter direction selector)
Output Y: Logic High (to be used as counter disable)
"Transform" button pressed:
Output X: Logic Low (count up)
Output Y: Logic Low (counter enable)
"Untransform" button pressed:
Output A: Logic High (count down)
Output Y: Logic Low (counter enable)
That's the point where I slam into a wall... I've come up with half a
dozen different ideas, all of which fall apart when I start trying to
actually draw a circuit to implement them.
It seems to me that a couple of transistors would do the job, but I'll
be dipped if I can figure out how to wire the little beasties to make
what I want to happen, happen.
I'd go with pulling directly from the H-bridge controls, but most of
this board (the whole thing is less than a square inch) other than the
power/antenna/output connections is surface-mount stuff, and I've
literally got no room to tap a wire in to grab the signal I need.
So, I turn to the group and hope somebody can help me out of this jam.
Anybody?
controlling four phases of a stepper - Input goes to logic low, the
corresponding stepper phase goes "hot", while the other three phases
either stay, or go, as needed, "cold". That's good.
I've also got my sequencer working - Oscillator oscillates, feeds
counter's clock pin, counter counts either up or down according to the
state of the direction pin and enables, output of counter feeds a 1-of-4
decoder, decoder connects to the four inputs of the driver, and
everything works - Pull the counter's direction and enable pins to low,
and watch the stepper step clockwise. Pull the direction pin high and
the enables low, and watch it step counterclockwise. Pull the enables
high, and watch the stepper hold position - Exactly as planned. Yay! I
love it when a plan comes together!
Now, I want to make controlling it wireless...
I've got an el-cheapo ($6 on sale at RatShack) R/C car controller with 6
"functions" - forward, reverse, left, right, transform, and untransform.
It drives three small PM motors (set up to drive two of them together -
one clockwise, and the other counterclockwise for forward, vice-versa
for reverse, both clockwise for left, and both counterclockwise for
right, plus a third that gets driven clockwise/counterclockwise for the
transform/untransform function) via three separate H-bridge circuits,
one per motor.
The existing module is presently set up to run on a 3.6V NiMH
micro-pack, but after chasing down datasheets, I find that all the
"active" components on the board are rated to cope with maximum ratings
of anywhere from 15 to 60 volts, depending on exactly which component I
happen to be looking at. In other words, I expect I'll have no problems
with smoke leaking out of anything if I try to run it on 5, or even 12,
volts instead of the 3.6V battery pack it currently uses. In light of
that fact, I did some testing, and found that it works just peachy on
the 5 volt supply I've already got handling the sequencer/low-voltage
side of the driver (which is coupled to, but isolated from, the 12 volt
"high power" side of the board by 4n26s on each input) which should mean
I'll have two +/- 5 volt (minus any junction drop that comes into play)
outputs available from the R/C board.
As things stand, I'm planning on working with the lone
"transform/untransform" motor output as the simplest, which means I'll
have two connections - let's call them "A" and "B".
Here's what I get when I meter A and B:
No TX button pressed:
A = 0V
B = 0V
"Transform" TX button pressed:
A = +Vbat
B = -Vbat
"Untransform" TX button pressed:
A = -Vbat
B = +Vbat
Hardly surprising from an electronically switched H-bridge, huh?
I need to turn that into two independent logic outputs, "X" and "Y",
like so:
No button pressed:
Output X: Irrelevant (to be used as counter direction selector)
Output Y: Logic High (to be used as counter disable)
"Transform" button pressed:
Output X: Logic Low (count up)
Output Y: Logic Low (counter enable)
"Untransform" button pressed:
Output A: Logic High (count down)
Output Y: Logic Low (counter enable)
That's the point where I slam into a wall... I've come up with half a
dozen different ideas, all of which fall apart when I start trying to
actually draw a circuit to implement them.
It seems to me that a couple of transistors would do the job, but I'll
be dipped if I can figure out how to wire the little beasties to make
what I want to happen, happen.
I'd go with pulling directly from the H-bridge controls, but most of
this board (the whole thing is less than a square inch) other than the
power/antenna/output connections is surface-mount stuff, and I've
literally got no room to tap a wire in to grab the signal I need.
So, I turn to the group and hope somebody can help me out of this jam.
Anybody?
