Gee, I thought motor cycling would be Harleys or Hondas.
Since the three time values you mention are all multiples of 100 mS, how about the solver of all problems, the 555 set to 100 mS and a counter/decoder to get the on/off/delay times?
GG
Why? What are the consequences of continuing to power the motor when it is up against an end? I'd expect that there would be several consquences, perhaps including a destructive one or two.
And while we're asking questions, "How?" How do you know where the limit is so you know when to delay and reverse?
If you really don't want to use any kind of sensors (like if you are in a pit full of sewerage or something :-), you could monitor the motor current and stop/reverse the motor when it reaches something approaching stall current. That scheme has the added benefit of protecting it from other faults as well.
The more modern method of doing this is to use an "H-bridge" with four power transistors (bipolar or FET).
You may need more than a single bistable. Logically, you need a "quadstable": 1 = forward, 2 = R-delay, 3 = reverse,
4 = F-delay (and then back to 1). I think it could be done with a pair of J/K FFs, a couple of monostable MVs, and a few gates.I'm making heavy weather of what should be a fairly simple design. Taking the simplest case first. I want to run a mechanism with a DC motor (say 12V, up to 15A stall current) between fixed limits, constantly cycling: forward, reverse, forward, etc. Typically 500 ms in each direction. I'd welcome alternatives, but one way is to use NO microswitches at the limits to set and reset a bistable, whose output drives a DPDT relay, hence controlling the direction of current through the motor.
But now the harder case. What's the simplest way to add separate short pauses, say 100 ms at the forward limit and 300 ms at the reverse limit?
-- Terry Pinnell Hobbyist, West Sussex, UK
Vcc ! o / ! ---- +----------! \\ ---- ! ! NOR >-+---+-----------! \\ / ---! / ! ! ! NOR >--- To power device \\ ! ---- ! ---/\\/\\/-+-! / / ! ! ! ---- \\ \\ ------- --- ! \\ / --- GND / ! / \\ GND Vcc / \\ ! ! ------- o ! ---- ! / ---! \\ ! ---- ! ! NOR >--+---+-----------! \\ +----------! / ! ! NOR >---To power device ! ---- ---/\\/\\/-+-! / / ! ---- \\ --- / --- \\ ! ! GND GND
-- -- kensmith@rahul.net forging knowledge
Indeed. I have worked on projects where it was undesirable (or impossible) to use microswitches to sense the endpoints. I thought this was one of those projects. Duh!
Yeah - didn't notice that ambiguity until this morning .
Well, yes, a 555 could contribute, but that still leaves a lot you haven't mentioned! And anyway I'm hoping that simple RC sections could form the timing elements, without resorting to the complexity of monos or counters. No precision is necessary, as I hoped I'd implied.
-- Terry Pinnell Hobbyist, West Sussex, UK
Not sure what you're talking about here. Obviously, by 'pause', I mean STOP. No motor power.
I don't think you can have read my post properly. MICROSWITCHES are the sensors. I suppose sensitive current limiting might be a feasible example, but why not use the obvious choice?
Yes, I can do it with enough logic gates, but I'd hoped for some more elegant and simple solution. Maybe just one SPDT relay, 2 microswitches, two crude RC filters ... and some inspired logic!
-- Terry Pinnell Hobbyist, West Sussex, UK
Many thanks, that looks highly promising - I'll have a play with it and report back.
-- Terry Pinnell Hobbyist, West Sussex, UK
But could you first clarify what you have in mind for the driver circuitry please? Clearly it cannot be the single DPDT change-over relay used for the 'simple' case. That wouldn't accommodate any stops. Do you propose a second 'On/Off' relay? Or an H-bridge? Or...?
-- Terry Pinnell Hobbyist, West Sussex, UK
Easy microcontroller job. Drive the motor through an H bridge, or two relays if you think they will last long enough. The rest is software.
Paul Burke
I read in sci.electronics.design that Terry Pinnell wrote (in ) about 'Motor cycling between limits', on Sat, 20 Aug 2005:
'NO microswitches' doesn't mean 'no microswitches'.
What with 'motor cycles', it must be Ambiguity Week at Pinnell Towers. (;-)
-- Regards, John Woodgate, OOO - Own Opinions Only. If everything has been designed, a god designed evolution by natural selection. http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk
---
+V | [R] +----------------------A | | and Y---> REV +--------A | +--B | nand Y--+---+--[C]--+------A | ___ | O +--B | | nor Y--+ FWD | O | | [R] +--B | | | A--+ | | +--B GND +--Y nand GND | and Y---> FWD | | B--+ +----------------------A ___ | O | | | | REV | O +-----------+--[C]--+---+ | | | +-------------+ [R] | | [R] GND | +V:-)
-- John Fields Professional Circuit Designer
--
Oops, I didn\'t notice the requirement for asymmetrical pauses:
+V
|
[R]
| +--------------A
+--------A | and Y---> FWD
| nand Y--+---+--[R]--+------B
___ | O +--B | |
FWD | O | | [C]
| | A--+ |
GND +--Y nand GND
| | B--+ +--------------A
___ | O | | | and Y---> REV
REV | O +-----------+--[R]--+------B
| | |
+-------------+ [C]
| |
[R] GND
|
+V
Guilty as charged for 'motor cycles', your Honour. But innocent on the lesser charge of 'NO microswitches', on the grounds that its context made my meaning obvious.
But thanks, I see now where Richard was coming from .
-- Terry Pinnell Hobbyist, West Sussex, UK
-- Yup, Good one. You also have to go high true on the switches.
--
Either, actually, since the truth table looks like this:
FWD REV
FORWARD 1 0
REVERSE 0 1
PAUSE 0 0
Here\'s the latest schematic, with Ken\'s suggested modification:
+V
|
| O
FWD | O
| +-------------------A
+--------A | nor Y---> FWD
| nor Y--+---+--[R]--+-----------B
[R] +--B | |
| | | [C]
| | A--+ |
+---+ +--Y nor GND
| | | B--+ +-------------------A
GND | | | | nor Y---> REV
[R] +-----------+--[R]--+-----------B
| | |
+-------------+ [C]
| |
| O GND
REV | O
|
+V
"Terry Pinnell" a écrit dans le message de news: snipped-for-privacy@4ax.com...
Some high tech solution:
add some play between the motor/actuator and its load so that once the motor has just reversed the load starts moving 200ms later. Then adjust your microswitches positions one to +50ms, the other to -50ms.
You could adjust the motor speed so that the 200ms corresponds to 555 (um).
-- Thanks, Fred.
In article , Terry Pinnell wrote: [...]
A full H bridge would be the way to go in this case.
-- -- kensmith@rahul.net forging knowledge
In article , John Fields wrote: [...]
Transpose to NOR gates and you get the "high = run" polarity with just one package.
This is a good job for CD4000 logic. They make enough swing to drive power MOSFETS.
-- -- kensmith@rahul.net forging knowledge
Thanks, John, looks good. Are you assuming an H-Bridge driver section, rather than relays?
-- Terry Pinnell Hobbyist, West Sussex, UK
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