# three phase motor control with limit switches

#### rmas308

Joined Oct 7, 2018
6
Hello all, I am in some need of guidance. I've been tasked with building a moving target system for the local hunting club.
Most commercial units run 6000 to 10000 dollars, and being a welder by trade I'm pretty handy with fabrication.
I have everything but the circuit to control the toward and reverse of the motor figured out...
1)The system is basically a target pulled along a track with a pulley system.
2) the wire is attached to the trolley which is looped through a sheave on a motor which pulls it down and back along the track
3)forward and reverse are activated by an ear on the trolley hitting a verticle wobble type limit switch. On initial energization of the motor the trolley will go down the track, hit the limit switch, then come back and hit the second limit switch, then go back down the track(back and forth)
4) There is a delay (several seconds) from the time the limit switch is closed to allow the target to stop traveling as not to put stress on the motor before reversing
5)motor speed is set by a motor controller

attached a couple pictures of another build that I'm basing it on... i realize this is my first post... I'm new to the electronics works... be gentle

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Joined Jul 18, 2013
20,435
Is it truly a 3ph motor you are thinking of using?
If so what is the nature of the supply? Voltage? etc
Max.

#### rmas308

Joined Oct 7, 2018
6
I have access to single or double phase motors. My cohort in this father owns a electrical shop. the power supply will 115v from a generator since this is a mobile system.

#### KeepItSimpleStupid

Joined Mar 4, 2014
4,010
You won;t like single phase. Two phase might be "split phase"?

and look up Idec smart relay. There is a simulator for it.

I'm not saying that these will go together, but it's an approach. You get speed control and braking. You may not even need the smart relay.
It automatically has Fwd/Rev dead time built in.

You might, say use a dual coil latching relay to set the direction.

There are VFD's that will take 120 V in and create 208/240 V 3 phase out.

Sizing generators can get tricky with motors.

#### BR-549

Joined Sep 22, 2013
4,938
What is the weight of the trolley? Are you satisfied that it will handle wind and projectile load?

#### Picbuster

Joined Dec 2, 2013
996
Hello all, I am in some need of guidance. I've been tasked with building a moving target system for the local hunting club.
Most commercial units run 6000 to 10000 dollars, and being a welder by trade I'm pretty handy with fabrication.
I have everything but the circuit to control the toward and reverse of the motor figured out...
1)The system is basically a target pulled along a track with a pulley system.
2) the wire is attached to the trolley which is looped through a sheave on a motor which pulls it down and back along the track
3)forward and reverse are activated by an ear on the trolley hitting a verticle wobble type limit switch. On initial energization of the motor the trolley will go down the track, hit the limit switch, then come back and hit the second limit switch, then go back down the track(back and forth)
4) There is a delay (several seconds) from the time the limit switch is closed to allow the target to stop traveling as not to put stress on the motor before reversing
5)motor speed is set by a motor controller

attached a couple pictures of another build that I'm basing it on... i realize this is my first post... I'm new to the electronics works... be gentle
Use a PID controller like MX2 allowing to switch backwards, forwards, wait between,slow start and slow stop.
Prices depending on power and model price 100$to XXXXX$.

Picbuster

#### rmas308

Joined Oct 7, 2018
6
What is the weight of the trolley? Are you satisfied that it will handle wind and projectile load?
trolley weight is approximately 50lbs. It will handle most projectiles past 200 yards believe it or not

Joined Jul 18, 2013
20,435
Use a 3phase rectifier bank and use a DC motor such as ex-treadmill types etc, with appropriate gearing, which I assume you will need, you should have adequate torque needed.
You will probabally need to also build a small electronic enclosure for the control electrics.
Max.

Joined Jan 15, 2015
5,360
All things considered I doubt you need a 3 HP or 3 Phase motor. You are only dragging a 50 Lb trolley back and forth on a track. Likely a small DC fractional HP variable speed motor with a suitable gear ratio will do just fine. A 50 Lb trolley on a stainless steel bed with decent ball bearing casters is all you need. You can look to suppliers like Grainger for the motor and motor controller. I would use standard parts for a few reasons. The first is by using a standard motor and controller parts are easily replaced if you are not around. You also mention 200 yards max so I assume these guys will likely be shooting NRA High Power out to 200 yard line. I suggest you check with the club as to if they shoot in rain or if the target trolley will ever get wet. I have shot competition in the rain. Also, determine a budget? Some clubs have money and some not so much. While you do not need a \$5,000 target system you want something reliable and easy to maintain and setup.

I would also consider just making a target frame where standard targets are fitted on a cardboard backing. I would use angle iron (stainless) which can easily be replaced because as sure as God made little green apples someone will manage to shoot the frame and it would not suprise me if they also manage to shoot the box containing the motor, controller and assorted guts. Using a standard pre fabricated controller also allows for you to easily add a relay and some simple wiring for your reversing circuit. Just make sure you well protect everything in the box because like I said somehow, someway, someone will shoot it, been there and have seen that.

Ron

#### BR-549

Joined Sep 22, 2013
4,938
I don't know your environment or situation...but.....a "clothesline" pulley system might have advantages over a tracked trolley. Both with cost and maintenance.

#### BR-549

Joined Sep 22, 2013
4,938
The ideal moving target would have "home" at 200 yds. Target trajectory would be 45 degrees to shooter and end at 250(or 300) yds. Then add a + or -, 30-40 ft of elevation to endpoint also.

When your riflemen can hit that target coming and going.......then move home to 400 yds. and repeat.

An inline moving target at distance is a challenge too.

#### rmas308

Joined Oct 7, 2018
6
The reason for the continuous travel of the trolley is so speed can be set and the shooters can move back to the firing line X distance away. Like reloadron said, I'm trying to put this thing together with parts and electronics that are somewhat available... because someone will...inevitably shoot it.

#### rmas308

Joined Oct 7, 2018
6
Wouldn't the continuous toward and reverse of the motor and the delay before motor energization all be accomplished with a motor controller, two spdt limit switches, and a time delay dpdt relay?