Automatic round movements

Thread Starter

Haropas

Joined Aug 16, 2019
51
I have a dc motor installed to a turntable.
Is it possible by using a limit switch to make it stop and start again only by unplugging the motor and plugging it again ?

By that I mean i will have a timer switch programmed to giving power to the motor a specific time for five minutes (because i can't program it for less than 5 minutes)

So when the time comes from the timer switch the motor will start turning the turntable clockwise and i want to stop the turntable in a specific place by putting a limit switch and turn off the motor.

The turntable will remain there in the exact spot even if the timer switch is giving power because we set it for five minutes and the motor worked for a couple of seconds.

After couple of minutes the timer switch will stop giving power untill the next day the same time and for five minutes again.

By using a relay or something similar i want when the time comes and the timer switch give power again I want the turntable to disengage the limit switch and turn clockwise untill it meets again the same limit switch and stop for another 24 hours

I dont know if this is a science fiction diagram that i am asking...

Thank you in advance
 

MaxHeadRoom

Joined Jul 18, 2013
25,990
One issue may be exact position stopping and also remaining in the position if the TT is free to revolve with no power.
More details on the TT mechanism(s) , gearing etc, would help.
 

LowQCab

Joined Nov 6, 2012
2,506
A "Turntable", as in, the thing that plays Vinyl-Records ?
If so, that's a very weak Motor, designed for extreme smoothness,
and maintaining a specific RPM.

It would be a big help if You would explain, in detail, what the purpose of your project is.
This is an almost universal problem in these Forums ......... Not enough information.
If You don't provide enough information,
what You will get is a bunch of retired Electronics-Engineers
standing around the Water-Cooler,
telling stories about astounding things they did 30-years ago.

I'm guessing You need a Stepper-Motor.
.
.
.
 

Thread Starter

Haropas

Joined Aug 16, 2019
51
A "Turntable", as in, the thing that plays Vinyl-Records ?
If so, that's a very weak Motor, designed for extreme smoothness,
and maintaining a specific RPM.

It would be a big help if You would explain, in detail, what the purpose of your project is.
This is an almost universal problem in these Forums ......... Not enough information.
If You don't provide enough information,
what You will get is a bunch of retired Electronics-Engineers
standing around the Water-Cooler,
telling stories about astounding things they did 30-years ago.

I'm guessing You need a Stepper-Motor.
.
.
.
A "Turntable", as in, the thing that plays Vinyl-Records ?
If so, that's a very weak Motor, designed for extreme smoothness,
and maintaining a specific RPM.

It would be a big help if You would explain, in detail, what the purpose of your project is.
This is an almost universal problem in these Forums ......... Not enough information.
If You don't provide enough information,
what You will get is a bunch of retired Electronics-Engineers
standing around the Water-Cooler,
telling stories about astounding things they did 30-years ago.

I'm guessing You need a Stepper-Motor.
.
.
.
16622103038168455126113904249388.jpg16622103286406534512508368563513.jpg
The dc motor has enough power and its not a stepper motor but its actually a motor with gears so it doesn't turn really fast in order to have problems (60 rpm).

So in the first picture i have a top view and the turn table has a small bump that will trigger the limit switch. Ant the turntable will stop. Then the timer switch automatically will give power again in 24 hours and the motor will start again untill it makes a full cycle and engage again the limit switch. I hope the information is enough.
 

Thread Starter

Haropas

Joined Aug 16, 2019
51
Hi Haropas,

If I understand correctly, the problem you need to overcome is that when the turntable triggers the switch to turn the motor off then without a switch in parallel (i.e. a relay) to turn it back on again then the motor doesn't start again when the timer triggers Vdc after 24 hours. And the relay needs to be on long enough for the turntable to go beyond the stop switch. If it takes 2 seconds to go around, a time way less that 2 seconds should suffice to "escape" the stop switch and do just one turn.

Please see my attached sketch which I think might work. There are guys far cleverer than I who may tell me it won't work, or can improve/simplify it!

The idea is that Tr2 is initially turned on by the voltage Vdc x R4/(R3+R4) but the capacitor charges up through R1 which charges the capacitor so the voltage into the base of Tr1 turns it on which in turn grounds the base of Tr2 turning the relay off. Immediately I see a fault in my circuit! Not good to let the base of Tr1 to get to Vdc x R2/(R1+R2) - easily sorted if this is close to what you are looking for. R2 was initially intended just to allow the charge on the capacitor to leak away when Vdc is removed but the right selection of R1, R2 and C may actually be enough to protect Tr1

To stop the motor fast it would be nice if the stop switch could short the motor terminals

Hope this helps!
I gave more info in the previous reply if you want to check. The truth is that i have to give it some thought and study a little bit in order to understand it
 

Thread Starter

Haropas

Joined Aug 16, 2019
51
I gave more info in the previous reply if you want to check. The truth is that i have to give it some thought and study a little bit in order to understand it
And actually i want to use a relay if thats possible. I dont want to use an arduino.
 

MrChips

Joined Oct 2, 2009
27,137
Tricky problem.

When power is restored the cam micro-switch is in the home position.
You need to override the micro-switch with a timed circuit to re-enable the switch once the turntable is off home position.

Another solution is to use an electronic circuit that triggers on transition, i.e. open-to-close, and not on levels. You would need some transistor or IC circuits to do this.
 

strantor

Joined Oct 3, 2010
6,112
The simplest, 1-relay circuit I could come up with is below. It requires a dual-coil latching relay, two capacitors, and two resistors. The capacitors create pulses to the coils, so that they only switch the relay when voltage is first applied. Thereafter voltage must be removed and reapplied to create another pulse.

20220903_124907.jpg

At time 0, the limit switch is against the cam, held closed, so C2 is charged. The dual coil relay CR1 is in the reset state, and no voltage is applied to the motor.

At time 1, the timer first turns on (TD relay contact), the set coil of CR1 is pulsed through capacitor C1, CR1 changes state, voltage is applied to the motor through the normally open contact of CR1, and the cam moves off the limit switch LS1.

As the motor moves around its circular journey, capacitor C1 charges and C2 discharges through R2, and...

At time 2, when it comes back around to 360 degrees and the limit switch is activated again, the reset coil for CR1 is pulsed through capacitor C2 and the relay changes state again.

It will stay in this state until..

At time 3 (a few minutes later) TD opens to drain capacitor C1 through resistor R1 and then...

At time 4 (24hrs later) TD closes again to send another pulse through C1.

Then the cycle repeats.

The tricky part would be finding the right values of capacitor for C2 and R2 that will pass enough current for long enough to trigger the reset coil, while still draining fast enough to be drained by the time the motor come back to home, and without causing too much constant current draw through R2.

The electronic circuits posted here earlier are probably better options but you asked for a simple relay circuit and that's kinda my thing. If this relay solution is the direction you want to go, this is a suitable relay.
 
Last edited:

LowQCab

Joined Nov 6, 2012
2,506
Haropas
Are You experienced enough to create a Perf-Board-Circuit ?,
or do You need to stick with mechanical Relays etc. ?

Does the Time need to be EXACTLY "24-hours" ?

Does the Device have to turn at an exact time of Day ?, even if AC-Power goes out ?

How precise must the "stopping-point" be ?,
is there some other part that must be in alignment with the Turntable when it stops ?

Are there any other "External-Events", ( beside the Time of Day ),
that could be used to trigger a rotation ?,
( such as Sun-rise, or Sun-set, or any other regularly occurring event ).

You haven't told us what this device is supposed to do,
what is it rotating ?,
why does the "thing", ( whatever that might be ), on the Turntable need to be rotated ?
.
.
.
 

Thread Starter

Haropas

Joined Aug 16, 2019
51
Haropas
Are You experienced enough to create a Perf-Board-Circuit ?,
or do You need to stick with mechanical Relays etc. ?

Does the Time need to be EXACTLY "24-hours" ?

Does the Device have to turn at an exact time of Day ?, even if AC-Power goes out ?

How precise must the "stopping-point" be ?,
is there some other part that must be in alignment with the Turntable when it stops ?

Are there any other "External-Events", ( beside the Time of Day ),
that could be used to trigger a rotation ?,
( such as Sun-rise, or Sun-set, or any other regularly occurring event ).

You haven't told us what this device is supposed to do,
what is it rotating ?,
why does the "thing", ( whatever that might be ), on the Turntable need to be rotated ?
.
.
.
Its just for an automatic pet feeder . So it doesnt matter if i dont have power for an hour or so, or i can use a battery. And yes the position should be precise. And i think with a transistor, a resistor ,a limit switch,the motor and a capacitor i can make it like a video i replied with in a previous answer
 

LowQCab

Joined Nov 6, 2012
2,506
This is a Mechanical problem first.
The type/size of the Food, and the volume it takes-up,
the weight and logistics of getting the Food to "flow" without jamming the mechanism,
the amount of space available, and lastly, how much power will be required to operate it reliably.

All of these things need to be worked-out first,
then an appropriate Gear-Motor can be selected,
and then, the Automation-Electronics for the Gear-Motor can be designed.

Are You feeding a Horse, or a Gerbil ?
.
.
.
 

Thread Starter

Haropas

Joined Aug 16, 2019
51
Fascinating to read about the Kearns wiper patent and that he has made millions from suing all the major automotive manufacturers! My circuit uses the same idea to turn Tr1 on, which then turns Tr2 off after a brief period and because Tr1 stays on whilst the power remains connected Tr2 remains off until the power is taken away.

I don't think it's practical to make your device work with just one transistor - If your power is on for five minutes you'd maybe have to charge a very large capacitor through a very large resistor to delay the motor start for three minutes so it would then do one rotation and stop again for three minutes, by which time the power would have turned off. So not impossible, but for the sake of a second transistor you get just one rotation as soon as power is applied. A string of diodes into the base of a single transistor would mean that the voltage on the capacitor would have to rise much higher than 0.6V which would allow the use of smaller values of resistor and capacitor for a single transistor solution if you are determined to have a go....
Thank you so much for all the help. I start to learn things whenever i am about to make something. I will study your circuit more because i am struggling a little because its my first time trying to make a circuit without the help of youtube videos. I have exams this period so my time is limited. Next month i ll try it and send the results.
 
i ll try it and send the results.
It works :) Had a spare twenty minutes, used a 25V 1000uF capacitor because I had one, with relatively low values of R1 and R2 (18K and 2K2 respectively) and the motor runs for about one second before stopping. Remove power to allow capacitor to discharge and motor runs again for a second when power is re-connected. To select the optimimum resistor values you should really know the current the motor needs, and the gain of the two transistors - I just winged it! If you look at the sketch of the circuit, I put a diode D1 between the collector of Tr1 and the base of Tr2 but it's not necessary - my prototype connects the collector of Tr1 and the base of Tr2 directly, as shown in previous sketches.

If you are working out how it works I recommend building the circuit with Tr2 and the two resistors from it's base and the supply rails and check that the motor runs. Then build the capacitor and its two resistors and see how the voltage rises on the capacitor when you switch on the power. Select the two resistors so that voltage reaches abour 1 volt. When that voltage reaches 0.6V it will turn on Tr1 which grounds the base of Tr2 turning it off.

When you come to build it and are not sure how to calculate component values, just ask.

1663239797226.jpeg


I
 

Thread Starter

Haropas

Joined Aug 16, 2019
51
It works :) Had a spare twenty minutes, used a 25V 1000uF capacitor because I had one, with relatively low values of R1 and R2 (18K and 2K2 respectively) and the motor runs for about one second before stopping. Remove power to allow capacitor to discharge and motor runs again for a second when power is re-connected. To select the optimimum resistor values you should really know the current the motor needs, and the gain of the two transistors - I just winged it! If you look at the sketch of the circuit, I put a diode D1 between the collector of Tr1 and the base of Tr2 but it's not necessary - my prototype connects the collector of Tr1 and the base of Tr2 directly, as shown in previous sketches.

If you are working out how it works I recommend building the circuit with Tr2 and the two resistors from it's base and the supply rails and check that the motor runs. Then build the capacitor and its two resistors and see how the voltage rises on the capacitor when you switch on the power. Select the two resistors so that voltage reaches abour 1 volt. When that voltage reaches 0.6V it will turn on Tr1 which grounds the base of Tr2 turning it off.

When you come to build it and are not sure how to calculate component values, just ask.

View attachment 276278


I
Yours is professional
Mine is crap and also doesn't work.
can tell from this scene what is wrong and what changes i should make ? Also i googled the transistors names on the internet in order to confirm that were NPN.
IMG_20220921_201647.jpg
 

LowQCab

Joined Nov 6, 2012
2,506
Before You concern yourself with getting a Circuit to work ..........
Can you manually make the Feeder work ?
There are far more simple ways to handle the Electrical part,
that is,
after You have a workable Machine.

Can You adjust the quantity of Food dispensed per rotation ?

Is that quantity of Food actually consistent, on every single cycle ?

Is it possible to jam the mechanism, and lock-up everything ?

Is the Motor powerful enough to reliably operate when
the Hopper/Storage-Bin is completely full of Food ?

How much Current does the Motor require when
the Hopper/Storage-Bin is completely full of Food ?

It seems that You are approaching this project in reverse order.
.
.
.
 

Thread Starter

Haropas

Joined Aug 16, 2019
51
Actually i had to change the Tr2 because it didn't work and it was KSP 44 -F30. So I changed it to a UTC C945L PSHA . So as you said i made the first picture with Tr2 only with a 2k resistor and it worked fine but when i connected the point A (base of the transistor ) to the negative wire nothing happened the motor continued turning. ( Actually i heard something like it was struggling but nothing really happened only a difference in the sound like some interference)


Just to add more info the motor is just a motor you find in the rc helicopters and i attached it to a synchronous motor myself making a really high torque low rpm motor and with 3.6 volts because my power supply actually starts from 3.6 and not 3 it has plenty of torque.)

Do you think is the transistors fault? Because i didn't buy them new i just had a broken inverter and i took the transistors from there. 16638465264478926970809673645598.jpg
First thing I notice is that you are only using a 3V power supply. So with your 10K and 2K resistors you are only putting 2 x 3 / 12 = 0.5V into the base of the transistor, not enough to turn it on. And you've used 10k resistors all round - they need to be calculated. I'd like to suggest that you start again, building the circuit in stages and testing as you go. Do you know the specification of the motor you are using - i.e. rated voltage and power? And what are the transistors you are using?

I'd recommend building the below first to check that the motor turns on when the current through R4 into the base of the transistor turns the transistor on. If you don't know the power of the motor maybe try R4 = 1K. The higher value you can get away with helps reduce the size of the capacitor you need and reduces overall current drain but too high a value will mean power is lost in the transistor which may burn out. If you know the motor details and the transistor gain you can work out a proper value for R4
View attachment 276737
With the motor running, temporarily connect point A to the negative rail. The base voltage drops to zero so the transistor turns off so the motor should stop. Then connect point B to the negative rail and the motor should come on again. These two actions are simulating what the other transistor and the switch are going to do respectively.

Next step would be to add Tr1 and resistor R1. The purpose of Tr1 is to ground the base of Tr2. If R4 is 1K then R1 can probably be 56K. Leave the connection between R1 and the positive rail open. The motor should run, then stop if you connect R4 to the positive rail at point C.
View attachment 276740
Next, add the capacitor. When you connect the power the motor should turn on briefly until the capacitor charges up to 0.6V turning Tr1 on which will ground the base of Tr2 which turns the motor off. If you disconnect and re-connect the power without discharging the capacitor the motor will hardly come on at all as Tr1 will turn on almost immediately.
View attachment 276744Finally, add R2 which allows the capacior to discharge. Another 56K resistor should be okay but the resistor values really need to be calculated based on the gain of the transistors and the motor power requirements. View attachment 276745
 
Top