Hobby motor controller to start and stop a lift moto

Thread Starter

DDEM

Joined Mar 27, 2024
3
I'm using 2 through beam sensors to trigger a relay to start and another relay to stop or reverse a 12 vdc hobby motor. Using NPN sensor output. One side of the relay coil is tied to the (-) power rail and the other side is tied to positive output (black wire) from the sensor.
I've wired it up but the circuit doesn't work. The motor draws 600ma, the sensors pull about 33ma, and the relay coils draw some but I'm not sure how much. My power supply is 12vdc @ 1 amp output. I've checked all of the wiring and it seems to be correct. I can drive the relay manually and it will switch but it won't switch using the input from of the sensors.
I'm using pcb relays to switch the power to the motor. The relays are 16 pin dip dpdt relays. Rated for 12vdc at the coil a contacts that are capable of handling up to 3amps on the contacts.
EG57_ 1580.png
 

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sghioto

Joined Dec 31, 2017
5,420
NPN output sensors are normally low side switching.
Try connecting the other side of the relay to the positive rail not negative.
 
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kaindub

Joined Oct 28, 2019
132
The sensors are wired correctly according to your sketch. But the relay will not hold in .
Its the logic of the power switching thats a problem
 

LowQCab

Joined Nov 6, 2012
4,199
Please provide the Spec-Sheets for all of the Components that You would like to use.

Please explain, in detail, exactly what this project will be expected to do when it is completed.

Please explain why the particular Sensor Part-Numbers were chosen for this project.

Please explain all of the actions that will start, or stop, motion in any particular direction,
along with which actions will be Manual,
and which actions will be Automatic,
and which actions could be both Manual or Automatic,
and the why for each individual Action.

Pictures could make this much easier.
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Jerry-Hat-Trick

Joined Aug 31, 2022
578
As already mentioned, it’s not exactly clear what you are trying to do but for this application, where your motor draws 600mA at 12V, I’d consider using an H Bridge IC rather than relays so you are only concerned with logic levels which draw low current
 

sghioto

Joined Dec 31, 2017
5,420
I believe the wiring diagram edited by the moderator is correct but the TS says in post #1 that one side of the relay coil is connected to the negative side of the supply not the positive which is most likely why the sensors will not activate the relays.
 
How would you like to run your lift, manually or automatically? I did a similar project for a toy lift (crane) I can post the circuit for you including all components required.
Cheers Henry
 

MisterBill2

Joined Jan 23, 2018
18,970
With the relay contacts wired as shown in the wiring diagram there is no possible way to reverse the motor. It can be reversed using those relays but with a much different arrangement of connections. The present motor power connection scheme is not correct in any aspect.

So if the intention is to have the motor drive something back and forth between two positions there is nothing in that circuit that will do it.
In addition, if the goal is to have the sensors operate the relays to drive in opposite directions in an alternating manner, the control scheme needs to be different. My experience with relays having that form factor is that they were FOUR pole, double throw. That contact arrangement may be able to provide what my guess is that you want.
Also, it has been only a guess by others as to what the connections to the optical sensors are, and how they function.
 
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Thread Starter

DDEM

Joined Mar 27, 2024
3
How would you like to run your lift, manually or automatically? I did a similar project for a toy lift (crane) I can post the circuit for you including all components required.
Cheers Henry
Please post your circuit and your component list. Thank you for the information!
 

Thread Starter

DDEM

Joined Mar 27, 2024
3
The current intention is to use this circuit to lift a Hot Wheels car from one level of the track to a higher level. What we need is to sense when the car is present then start the lift. When it reaches the top of the lift a second sensor will trigger the second relay to stop the lift motor.
We are building a very large installation of Hot Wheels track for the enjoyment of the kids in our family and wanted to automate the lift mechanism so we don't have to intervene to move the car up to the higher level of the track. We don't want to reverse the motor right now but sometime in the future we want to incorporate the reverse function.
We are trying to use parts that we have on hand. The challenge for me is to determine how to make this setup work.
I don't have any of the spec sheets on the components, just the hardware.
Thank you for your reply. DDEM
 

MisterBill2

Joined Jan 23, 2018
18,970
Without reversing the motor, how does the lift move to the lower level pickup position??? If load and unload are automated, possibly by gravity, the entire motion sequence could be automatic.
Like this:
1. Lower level, car rolls in via gravity.
2. Optical sensor detects car in place, (lift relay latches)
3. Lift elevates to unload level, stops, (lift relay unlatches)
4. lift gravity unloads, car rolls out.
5. Empty detected by top sensor (Lower direction relay latches)
6. Lift returns to lower level. Lower relay unlatches when level is reached.)

This could be a fully automated sequence, no human intervention except to clear misload and unload jam-ups.
 
Hi DDEM
See the attached drawing of a simple motor control for your project, I'm assuming that the lifting arrangement once is on upper level and the motor is de-energized it will come down by gravity, likewise the entry and exit of the car.
D1-Diode is there to prevent feedback into the Sensor out-put.
If you need further help, let me know Henry
 

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sghioto

Joined Dec 31, 2017
5,420
I'm not sure that arrangement will work with the sensors the TS is using.
NPN output sensors are normally low side switching.
 

MisterBill2

Joined Jan 23, 2018
18,970
It does not seem reasonable that a lift able to raise a small toy car will return reliably to the loer position by gravity alone.It also seems that there may need to be additional switches to sense that the lift is in position, aside from sensing that a car is in the lift.
 
If the sensors are PNP,re-arrange the circuit to suit polarities and remove the diode.
I agree that we are working on assumptions and most probably there is a need to incorporate more parts to the circuit.
DDEM, can you post a photo of the lifting device, maybe you need to install mini-limit switches and place the sensors in the correct location.
Henry
 

MisterBill2

Joined Jan 23, 2018
18,970
Certainly it will be easier to have the system work flawlessly if there are sensors or switches to detect when the lift is up or down. The one alternative is if the lift scheme uses a cam-operated lever to lift and lower the car platform.
I had not visualized that previously.
 
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