elevator doors

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regal009

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so, i m quite having a problem, its deadline is 13 hours from now.
this circuit will be used on a mini elevator doors to open or close]
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i have 3 monostable cascaded with . 1st MS triggers from another circuit, then its output is to 2nd monostable, then to 3rd.

i have 2 relays used to reverse the cd rom motor.

1st monostable drives the transistor that drives a relay, opening the cdrom
2nd monostable is waiting time.
3rd monostable is to drive another transistor-relay that will close the cdrom.

my monostable circuit is working fine with no relays but after i add transistors and relays, abnormalities starts to occur,

sometimes 1 monostable skips, sometimes , 2 monostable is high, sometimes it turns to a loop which should not be.

what suppose is the problem..
 
Have you placed diodes across the relay to protect the transistors from back EMF?

Can you show us your schematic..
 
Have you connected snubber networks (e.g. 0.1uF cap in series with 100R) across the relay contacts to suppress any voltage spikes?
Have you kept all wire/track lengths as short as possible to prevent spurious signal pick-up?
What is the supply voltage to (a) the monostables and (b) the motor?
Are the relay-drive transistors PNP or NPN type?
 
Last edited:
That's correct. I see you have a snubber across the motor, which is good.
BTW, I edited my last post. Please see the additional questions I asked.
 
well, while testing the circuit, i remove the dc motor guessing that that is the cause of problem, but still, abnormalities still occurs, by removing the relays, the monostables are working fine
 
I assume that the relays are rated 12V.
What current do the relay coils draw ( or what is the coil resistance)?
 
Might be worth coupling each pin 5 to ground via a respective 10n cap to prevent spurious signal pick-up?
 
Using the same power supply for the 555 monostables, relays, and motor can cause a lot of problems. The supply voltage may be dipping when the relays are pulled-in and the motor starts. This can cause problems with false triggering and timing. Liberal use of bypass capacitors across the 555's power pins can help. Separating the relay and motor ground returns from the grounds for the timing circuit is also important.

Ken
 
Last edited:
im currently remaking my 4-floor mini elevator.,
so far so good, used optocoupler to completely seperate relay and motor to my control circuit..
 
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