Automatic round movements

LowQCab

Joined Nov 6, 2012
2,357
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.
.
.
.
 
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
1663839336831.png
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.
1663841729684.png
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.
1663844023714.pngFinally, 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. 1663844227268.png
 
Last edited:

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
 
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.)
My component values were roughly based on the thinking that you are using an 8V motor as shown in your original diagram. The problem with a lower voltage motor is that it will draw more current to deliver the same power. I think you mean you connected it to a gearbox, not a "synchronous motor"? Anyway, you may have blown the transistor because it may not withstand the collector emitter current demanded by the motor. If you remove R4 does the motor still run?
 
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 ?
Giving this further thought, I don't thnk using a rc helicopter motor is a good idea. They are designed to spin really fast, approaching no load speed. When trying to do work I imagine they take a fairly high current, running slowly compared to when they have a propeller spinning at high speed. As LowQCab says, apart from looking at the overall mechanics, the key is to determine if the motor/gearbox combination will do the job, and you could do with knowing the current it draws. Consider something like https://www.ebay.co.uk/itm/393460009320 which looks like it is geared down to spin once in 1.5 minutes.

Also, when you start the motor with the transistor it will draw a high current as it's virtually a short circuit. I used a power transistor - BD131 which has a fairly low gain of about 20 but driven hard on it can take 3A current and withstand 15W power dissipation - it's only on briefly so no heatsink. Hence the need for a lowish value of R4. For example, if the motor takes as much as 1.0A the current into the base would need to be 50mA - with an 8V supply and 0.6V base/emitter voltage this suggests R4 = 150 ohm. I got away with R4 = 1K because the motor will start at a lower current although that may not be sufficient to drive your load, and it means the transistor is not driven hard on, so it will dissipate more power. Best bet is to use a Darlington Pair power transistor which may have a gain of around 1,000. They are simply a pair of transistors in one three pin device which uses a low current high gain transistor to turn the high current low gain transistor on - so the gain is roughly the product of the two gains.

In summary, selection of motor/gearbox is critical. Check it drives your system first, especially when it sees your worst case load. I expect a 12V motor with a high reduction ratio gearbox will be fine but I would not recommend a lower voltage motor.
 
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