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Time delay for 12V motor using 555 IC

Discussion in 'Homework Help' started by edmondcjj, Jul 17, 2017.

  1. edmondcjj

    edmondcjj Member

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    Hi i am a student and currently doing a project and i have very little knowledge about circuits and electronics. So, i would like if someone can help me on this circuitry that i needed to do. First i am required to operate a washing agitator through vibrations using a 12V motor and i have a 555IC , capacitors, resistors, a switch and a 9V battery. I am required to create a "time delay" so that when i press the switch to On the motor it will run and without me pressing the button again to switch it off it will stop on its own after like 25secs. The pictures below is what i have researched on so far and tried connecting it, it is supposed to give a timeout of about 26secs. However after testing it , it is not consistent. Also, when i press my switch to start the motor, it works however when i press again to stop the motor , sometimes it still continues running. So is there any way i can solve the problems? Thank you guys in advance. I do say i am really a beginner in this. IMG_2233[2].JPG IMG_2234[1].JPG
     
  2. alec_t

    alec_t Well-Known Member Most Helpful Member

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    Welcome to ETO!
    A few things to consider :-
    1) Have you checked that the motor stall/start-up current is less than 200mA (the maximum current a 555 is rated for)?
    2) A motor has considerable inductance. Read up about back-emf voltage spikes and precautions you can take.
    3) What makes you think pressing the button a second time should stop the motor?
    4) Always post a schematic of your circuit.
     
  3. edmondcjj

    edmondcjj Member

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    Sorry like i said i am a student and i thank you guys for ur kind understanding. I dont uds all those terms u have used.
    1) The motor is able to run however, sometimes it stops at around the time it is supposed to stop at and sometimes it doesnt.
    3) I dont know whether isit possible but thats what i want in my product, being able to stop the motor after pressing the ON/OFF switch like those one-way operation. if u get it :)
    4) I do not know how to draw one tho. i dont know how to read it too. the circuit i made above is based on reports and research and what i wanted to change from theirs is that to add a switch to allow it to on/off the motor whenever i want.

    Thanks alot for ur help tho. i am having trouble with my project and cant seem to fix the problem after countless research, in the end i decided to try using this forum as i believe is one of the more known technological forums.
     
  4. dave

    Dave New Member

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  5. alec_t

    alec_t Well-Known Member Most Helpful Member

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    Can you post links to that?
     
  6. cowboybob

    cowboybob Well-Known Member Most Helpful Member

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    Using the below pic, what are the values of the indicated parts?
    upload_2017-7-17_11-3-38.png
    Cap(s) will have a number followed by "μF". The Resistor will have colored bands.

    Normally, a "One-shot" 555 circuit will have only ONE cap where your circuit has 2 (as shown below).

    Also, when "bread boarding" a circuit such as yours, you have to be very careful that each component's leads (wires) are making good connections with the contact(s) of the board. Make sure the polarity symbols, if present, (+ and -) of the caps are attached to the correct bread board terminals.

    This is an equivalent schematic of your circuit (values are intentionally absent):
    upload_2017-7-17_10-56-48.png
     
  7. edmondcjj

    edmondcjj Member

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    Hi thanks alot for the reply.
    I am using a 10k ohm resistor on the left side and a 51k ohm resistor on the right. As for capacitors the top 1 is 47uf and the bottom one is 0.01uf. This i suppose is supposed to give a time out of around 26secs.
    Thanks for the schematic diagram u have showed me.
    I would then like to ask if those i stated like having the motor to start and stop accordingly on whether did i on/off the switch. and mind if u can help me check if my circuit is arranged properly? Because i get inconsistent timeout readings. Thank you!
     
  8. edmondcjj

    edmondcjj Member

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    Sorry, i dont really have links to it as it was done by a previous student and i am supposed to continue with his project.
    and from his report but i believe he has posted a thread too here regarding his circuits and i was following it.
    http://www.electro-tech-online.com/threads/i-need-help-with-my-monostable-circuit.150813/page-5
    However, what i want to improve or change on is the stopping of the motor based on the 26secs timeout. and being able to manually off the switch.
     
    Last edited: Jul 17, 2017
  9. edmondcjj

    edmondcjj Member

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    upload_2017-7-18_10-47-34.png

    This is his circuit which gave a timeout of 26secs. However it does not stop when I replace the push button switch to the normal push button switch i used at the thread picture i posted when it is pressed again.
     
  10. alec_t

    alec_t Well-Known Member Most Helpful Member

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    Using the same push button to start the timer and to stop it prematurely would involve a more complex circuit. Are you allowed to use a separate switch to stop the timer?
     
  11. edmondcjj

    edmondcjj Member

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    In this case do u have an idea on how i should arrange my circuit for it to be like?? I do not think having 2 switches 1 to off and 1 to on would be feasible. As it is troublesome for the user to operate the product i guess. As i am suppose to design a fruit and vegetable washing agitator and which slowly i have to move on having a proper sellable product. So for now im doing the electronics part. so i think having 2 switches bring inconvenience as now alot products already have one-way operations

    So, best would be having the same switch to start and stop the motor whenever the user wants and also if the user forgets to off the switch it will have a timeout after 26secs which saves electricity and power. Thank you!
     
  12. cowboybob

    cowboybob Well-Known Member Most Helpful Member

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    This is a self triggering, 29sec, monostable delay timer circuit. Pressing the push button once "latches" it in the ON position. The timer output will remain on for the time duration set by the 2 caps and the 51k resistor. To restart the timer, press the switch once to turn it off and then again to turn it back on.

    If at any time during the ON delay period you wish to terminate the output, just press the switch to turn the timer OFF
    upload_2017-7-18_18-11-4.png
    You'll have to find a SPST "Latching Push ON - Push OFF" switch, like this. The added diode (in this case, a 1N4148) is for rapidly bleeding off the 2 caps between power application(s) of the timer. This will maintain the accuracy of the delay timing when re-powered (everything starting as close to zero as possible).

    Other than this circuit, there are no 555 latching timer circuits whose output can be toggled between On and OFF with only one SPST switch.
     
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  13. edmondcjj

    edmondcjj Member

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    Sorry, but to clarify those u said. Does this means that I have to press the switch to start the motor and when i press the switch again it will stop whether or not the 29secs have passed? So, even if i leave my switch on, after 29secs it will stop? Also, even if for example i let it run for 10secs thn i off it and on it back again does the 29secs restarts?
     
  14. edmondcjj

    edmondcjj Member

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    Also, is it possible that i use this switch ? or it has to be the one u stated?
    Sorry, but do u mind showing me how to connect it on a bread board? I am still new to electronics and i dont know how to read a schematic diagram properly. Especially the wire pins its confusing. I really do thank you so much , would really appreciate it!
     

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    Last edited: Jul 18, 2017
  15. cowboybob

    cowboybob Well-Known Member Most Helpful Member

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    Yes.
    No. The new switch is a "latching" type. What that means is when it is first pressed, it is turned "ON" and it stays ON (is "latched" in a "down", or ON position) until it is pressed a second time, which releases the latch, allowing the button to rise, placing it in the OFF position. And ANY latching SPST switch will suffice. The one I suggested was simply the best, in this case, of the many available.
    Working on that now. I'll post it later.
     
  16. edmondcjj

    edmondcjj Member

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    How do i know whether the current switch im using is a SPST switch? my switch currently sounds similar to what u said i think hahah

    Thank you so much!!!! really appreciate that u are taking ur time to help me!
     
    Last edited: Jul 19, 2017
  17. cowboybob

    cowboybob Well-Known Member Most Helpful Member

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    Single Pole Single Throw switches have only two connectors.

    Latching SPST switches also only have two connections, but the button itself, when pressed down (which often makes a "click" sound with each pressed) will remain in the down position (ON) until pressed again, releasing the latch (again clicking) and returning to the up or OFF position.

    Note differences between old:
    upload_2017-7-19_12-46-57.png
    and NEW
    upload_2017-7-19_12-47-36.png
     
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  18. edmondcjj

    edmondcjj Member

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    The switch im using does have the click sound and remains in a pressed position when pressed and the goes back up when pressed again.
    This is the switch i am using currently.
    http://sg.element14.com/zf-cherry/k...e&ddkey=http:en-SG/Element14_Singapore/search
    Sorry but what do u mean by putting the switch between red battery lead and same formal position as the board.
     
    Last edited: Jul 19, 2017
  19. edmondcjj

    edmondcjj Member

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    Last edited: Jul 19, 2017
  20. edmondcjj

    edmondcjj Member

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    For the 1uf capacitor do i use the 35V or 50V?

    Also, just curious if i do not put in the diode in the circuit will it still work? Since the diode helps to gives accuracy of the time delay timing , or will the circuit not work at all? Because i do not have the diode now , however i want to try whether it will still work close to the 29secs at least.
     

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  21. edmondcjj

    edmondcjj Member

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    However now after i have added in the extra capacitor i test my circuit and it starts running on its on without me pressing on the switch.

    Also, does the leads of the battery like where it is placed matter? currently the black battery lead is on 3 row negative terminal and the red is on row 5 positive terminal.

    I do think that some how after connecting the capacitor it does not link to the switch thats why it starts on its on once i plugged in my battery?
     
    Last edited: Jul 19, 2017

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