Continue to Site

Welcome to our site!

Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

timed reversal of DC motor

Status
Not open for further replies.

leslcd

New Member
hi folk

i am new to this so please bear with me.
i am trying to get a motor to start up travel a distance then when it hits limit switch the motor stops and waits 5 seconds then reverses where it hits lower limit switch and then stops. this procedure then repeats whenever power is applied, i am using a small 12v motor as a demo just to provide proof of concept to people than it can be done.
 
Maybe you could try something like the thing I've attached. When power is applied, the top relay drives the motor forward. When the motor hits the limit switch, the top relay latches itself on, and the motor stops. With the top relay on, the lower circuit is provided with power - the 555 timer circuit turns the lower relay on when its timing capacitor charges sufficiently. With the lower relay on, the motor reverses until it hits the home switch, which turns off power to the lower circuit and stops the motor.

Hope this helps.
 

Attachments

  • relay.gif
    relay.gif
    33.4 KB · Views: 269
tried that and it did not work, just acted as though the timer was not present. started the project off holding the bottom limit switch and the motor turned cw as expected when it hit the top limit switch it then went ccw as it came away from the top limit it then reversed again and again in a never ending loop.
i will try to explain better what it is i am after.
i have been tasked with putting together a demo of the products we use and have pretty much got everything sorted but this motor problem. i have a relay board that is controlled by the software we use and we have the ability to switch relays on and off. i am so far controlling lights, door locks sirens etc etc, the usual stuff quiet easily but what the bigwig wants is for me to show that we can effectively control a barrier with the equipment by when tag enters the area the reciever picks it up and opens the barrier and after a set time the barrier would then close by its self to emulate the vehicle going over a loop as in real life. the problem i have is the time delay at the top limit is not working. i have had this working in the manner of the motor lifting hitting the limit and then lowering and hitting the bottom limit and thats is it but i really need the delay at the top end if possible.
all suggestions welcome
 
Last edited:
tried that and it did not work, just acted as though the timer was not present.
Um, it should work - unless your wiring's wrong or your test method's wrong (or my understanding of your question is wrong.. - it's designed to make the motor go forward until the 'limit' switch is hit, delay a few seconds, then reverse the motor until the 'home' switch is actuated).

started the project off holding the bottom limit switch
Just ignore the bottom 'home' switch for now. It's only used at the end of the cycle.

the motor turned cw as expected when it hit the top limit switch it then went ccw as it came away from the top limit it then reversed again and again in a never ending loop.
So the motor keeps ramming the limit switch turning it on/off/on/off (i.e. forward, hits limit, reverse, release limit, repeated)? If the top relay is wired correctly (the switched-ground contact going to the coil), after an initial press of the 'limit' switch, the top relay will activate and hold itself on until power is removed - therefore the motor cannot go forward again until the power is cycled.
 
Last edited:
will go through everything today to see if i missed anything and report back cheers
 
Last edited:
sorted out the bounce on the motor it now goes forward hit s limit switch then returns and stops at bottom limit. it just does not wait the couple of seconds at the top?
 
USE a H-bridge circuit, hook bases up to a flip flop, then put SET and RESET latches on your direction buttons,

using 2 DPST relays can make a H-bridge too.
 
Status
Not open for further replies.

Latest threads

New Articles From Microcontroller Tips

Back
Top