Project: 240v reciprocating saw circuit urgent help required please!

Discussion in 'Homework Help' started by HarrisonRedwood, Feb 9, 2016.

  1. HarrisonRedwood

    Thread Starter New Member

    Feb 9, 2016
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    Please help.
    My knowledge in electronics is not the best, for my A level engineering I am making an electronic can shaker using the motor from either an electronic drill or reciprocating saw. I need to be able to run this motor from a timer circuit where I can adjust the time its on for by using a variable resistor. The system needs to be able to plug into UK mains sockets and I am really stuck on how to design the circuit. Ideally I would like to use a 555 timer chip in my circuit and also incorporate a power on/off switch.

    Any help would be much appreciated in helping me design this circuit.

    Thank you very much and I will get back to all messages as soon as possible.
     
  2. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    Welcome to AAC!
    The mods may move this thread to the 'Homework help' section.
    Show us your efforts so far, so that we can point you in the right direction. We don't design the whole thing for you ;). Why is this 'urgent'?
     
  3. Wendy

    Moderator

    Mar 24, 2008
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    The 555 data sheet has schematics. Add a driver transistor and a relay and you will get there, Post a schematic and we will critique it.
     
  4. MaxHeadRoom

    Expert

    Jul 18, 2013
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    It sounds like you intend using a Universal motor from the sound of it, confirmation of intended motor needed.
    Why are you stuck on a 555?
    IF it is universal then you most likely need a Triac circuit.
    Max.
     
  5. HarrisonRedwood

    Thread Starter New Member

    Feb 9, 2016
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    Thank you for your reply. I will upload a schematic some time soon for you to critique, thank you for your help.
     
  6. HarrisonRedwood

    Thread Starter New Member

    Feb 9, 2016
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    It is not necessarily urgent but I am to a deadline. Ideally I would like to get it up and running by Easter so I have time for other improvements. Here is where I have gotten so far but my output at the moment is a buzzer and not the motor I intend to use. upload_2016-2-10_14-42-27.png upload_2016-2-10_14-42-27.png
     
  7. HarrisonRedwood

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    Feb 9, 2016
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    Here is where I am so far, it is not really working as the buzzer never seems to stop once it is on (the buzzer will be replaced by a motor) upload_2016-2-10_14-44-54.png upload_2016-2-10_14-44-54.png
     
  8. HarrisonRedwood

    Thread Starter New Member

    Feb 9, 2016
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    Hi, I am not stuck on using a 555 chip however they are very easy for me to access. I also cannot confirm the motor I am using as I don't have it yet however I might move to a smaller brushless type motor to reduce the voltages needed.
     
  9. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    Just use relay to power the motor and power the relay from the 555 output.
    You want it to turn OFF after a variable time has elapsed?
    Use relay.
    You want variable time? Use potentiometer in a single shot arrangement to set delay before 555 triggers the relay. You will need to wire the relay to self latch and power needs to be cut to reset the timer.
    So, motor is connected through an inactive relay and starts immediately upon power on. 555 starts counting at power on and then activates relay to stop motor. Relay stays latched until power is "reset".
    Also will need a 2nd relay(self latching) to keep motor from running at power on, until a Start button is pressed. This start button will initiate motor and 555 timer.
     
  10. MaxHeadRoom

    Expert

    Jul 18, 2013
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    There is no need to add the complication of a brushless motor, the simplest if going low voltage is a DC brushed motor.
    You mention a can shaker, any oscillation requirements of this nature would normally be done mechanically by a uni-directional motor rather than constantly reversing the motor.
    Max.
     
  11. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    In your schematic, pin 3 of the 555 is shorted to ground. That is bad for the 555 and will hold the buzzer on. Why is there a capacitor on pin 3? I think that cap is intended to decouple the supply, i.e be connected instead to both supply rails.
     
  12. HarrisonRedwood

    Thread Starter New Member

    Feb 9, 2016
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    Hi again, I'll take your advise and make a few changes. Hopefully it should work better then.
     
  13. HarrisonRedwood

    Thread Starter New Member

    Feb 9, 2016
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    My can shaker will work mechanically via a crank system. Therefore I will only need the motor to spin in one direction to drive it. The purpose of the circuit is to alter the length of time that it stays on for. And after more research I think I will likely go for the lower voltage dc motor.
     
  14. HarrisonRedwood

    Thread Starter New Member

    Feb 9, 2016
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    OK so what you are saying is to use a switch that turns on one relay that allows current to flow around the timer circuit, this will act as the main power on/off switch for the device. Then when the power is on I can use a potentiometer to set the time I want it running, then press a separate switch to activate the timer and begin its 'countdown'. As soon as that switch is pressed the relay going to the motor is activated and allows the motor to be on. Then once the time has run out the 555 circuit will deactivate the relay and current to the motor will stop flowing.
    I hope this is what you had in mind as I'm starting to build up a better idea of what's going. Finally can both the motor and 555 circuit be run from the same supply if a 240v to 12v transformer is used to power the circuit.
     
  15. MaxHeadRoom

    Expert

    Jul 18, 2013
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    A 12vac supply will amount to 16 v after rectification and smoothing, you can drive a 12v motor direct from the bridge output for 12vdc.
    If using a motor controller such as PWM then it is optional, as the PWM will control the rpm.
    Max.
     
  16. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    A quick sketch of my idea using relay logic. The motor can be any type or voltage since it uses an isolated set of relay contacts, but not too big, due to amperage limits on relay during motor start up.
    Two double pole double throw relays. Two momentary switches and a 555 timer circuit. 20160211_075005.jpg
     
  17. HarrisonRedwood

    Thread Starter New Member

    Feb 9, 2016
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    Hi, thanks for the sketch ill try and incorporate this into my future designs. I'm definitely going to go with the relay system as the moment as that seems to be the most logical answer. Thanks.
     
  18. MaxHeadRoom

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    Jul 18, 2013
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  19. HarrisonRedwood

    Thread Starter New Member

    Feb 9, 2016
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    Thanks this will be very useful. At the moment I'm trying to model my circuit on Yenka so that I have a variable timer circuit and a relay to the motor. I will post an image of what its looking like soon.
     
  20. HarrisonRedwood

    Thread Starter New Member

    Feb 9, 2016
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    I am really struggling to make a circuit that is able to supply a current to a device (LED, relay etc.) that will turn off after a set amount of time. Everything that I model on Yenka seems to either not work or just blow up. I've searched everywhere on the internet I can't seem to get any closer to making a working circuit.
     
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