7 Jun
2010
7 Jun
'10
12:50 p.m.
If you can
find one (and they're not rare on E-bay), get an HP59306 realy
actuator. This is a box containing 6 changerover relays controlled by an
HPIB interaface, the relay contains are wired to 18 4mm terminals
(binding posts, if that's what you call them) on the back. Assuming you
have some computer with an HPIB port, you can do computer control of
lights, small motors, etc very easily.
Well, that I don't have. Maybe the 1650 logic analyzer has it, but
I'm
not going to let him play with that just yet. But that's not a bad idea. Maybe I can find some
simple interface to a
USB port and build something to interface with a bunch of relays.
Maybe an old USB parallel port interface will do the trick.
I am told there's a USB-HPIB interface, but it's not cheap.
The advantage of the HP59306 is that it's a nicely boxed instrument with
easy to use terminals on the back for the relay contacts and front panel
switches/lights to operate and monitor the relays. You can test your
project using those and then try computer control.
2 Thoughts :
1) Lego Mindstorms :-)
I actually do have one of the early ones of these kits. Someone gave it
to me as a gift before the kids were born, but I've not messed with it
myself.
So that might be the way to go since he's already into legos. I'll dig
it out of the back of the closet. from the motors. I prefer servo systems..
2) _Old_ Fischertechnik. The new stuff is
somewhat dumbed-down with too
many single-function modules, etc, bnt the old stuff from the 1970s and
1980s is _very_ educational. The only problem is being able to afford all
you want...
Yes, being able to afford all he'd want is going to be interesting. Some of these kits are $300-$450. I'm not sure he
would need a 32 bit
processor controller when he's already got his own computer.
No, probably not. And that sounds like a modern kit. The older
electronics modules were simple functions, like a relay+driver, an
analogue comparator, a flip-flop, a monostable, AND gate, OR gate, etc.
You tended to need a lot of moudels to do anything, and they weren't
cheap...
If he gets that interested, I'll hack something up
with a PIC or Arduino
board and wire it up to relays or motors.
The first FT robot kit was just the motors, lamps, swtiches, pots and
standard mechanical bits. No electronics at all. You could buy
interefaces to then-popular micros (I have the BBC micro one, there was
certainly a C64 version), or you could do what I did and make your own.
Come to think of it, I'm sure I could dig up an old laptop and use the
parallel ports on that as a relay controller. Could fire up DOS and
write some simple BASIC programs to control relays via the parallel
port... yup, sounds like a plan. Would need some sort of platform with
motor controlled wheels to mount a laptop on top of... or maybe if I
could find a large toy tank and mount the laptop on top, since prebuilt
tank treads should be easier to control - would just take 4 bits. left
tread fwd/back, right tread fwd/back. Would need some logic to prevent
fwd/back from being turned on at the same time, but actually, could use
one relay for direction, and a second to turn the motor on or off, so it
wouldn't be possible to go fwd and back at the same time. Yeah, that
would work nicely... So 4 relays and two motors, and a few batteries.
After that we can add sensors, etc.
The easy way to control a motor with a pair of (changeover) relays is to
link the motor between the 2 common terminals (moving contact), connect
both NC contacts to battery -ve and both NO contacts to battery +ve. Then
if both relays are off, or both relays are on, the motor is not powered
(it's acutally short-circuited, which means you get some braking effect
when you use the relays to stop the motor which is a Good Thing). If one
relay is on, and the other off, the motor turns, the direction is
determined by which relay is turned on.
-tony