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

Thread Starter

HarrisonRedwood

Joined Feb 9, 2016
16
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.
 

Alec_t

Joined Sep 17, 2013
11,141
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'?
 

Wendy

Joined Mar 24, 2008
22,138
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.
 

MaxHeadRoom

Joined Jul 18, 2013
20,425
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.
 

Thread Starter

HarrisonRedwood

Joined Feb 9, 2016
16
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'?
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.pngupload_2016-2-10_14-42-27.png
 

Thread Starter

HarrisonRedwood

Joined Feb 9, 2016
16
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.
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.
 

Kermit2

Joined Feb 5, 2010
4,162
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.
 

MaxHeadRoom

Joined Jul 18, 2013
20,425
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.
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.
 

Alec_t

Joined Sep 17, 2013
11,141
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.
 

Thread Starter

HarrisonRedwood

Joined Feb 9, 2016
16
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.
Hi again, I'll take your advise and make a few changes. Hopefully it should work better then.
 

Thread Starter

HarrisonRedwood

Joined Feb 9, 2016
16
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.
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.
 

Thread Starter

HarrisonRedwood

Joined Feb 9, 2016
16
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.
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.
 

MaxHeadRoom

Joined Jul 18, 2013
20,425
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.
 

Kermit2

Joined Feb 5, 2010
4,162
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
 

Thread Starter

HarrisonRedwood

Joined Feb 9, 2016
16
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.View attachment 100465
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.
 

Thread Starter

HarrisonRedwood

Joined Feb 9, 2016
16
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.
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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