Gate Opener - 36vdc at 5Amps

Hi, I'd like to use an old C-Band dish actuator that runs at 36vdc and can draw almost 5A at full wind load (just before motor-stall) on the 12-foot gate. My knowledge of electronics is not great but have built lots of kits over the years, so know my way around a little.

Could I use... http://www.amazon.com/SainSmart-Stepper-Controller-Mega2560-Duemilanove/dp/B00AJGM37I/ref=pd_sim_147_10?ie=UTF8&refRID=00YCJCE0S23BJTWBAGSE

...to drive a bigger MOSFET to then drive the actuator?

If so, what would the circuit look like? Or, is there a better approach? if so, please elaborate.

I want to have motor-speed control so I can build soft-start and soft-stop into the code which I will be happy to share here. I want to work with the 36vdc as it takes almost a minute to open the gate and going down in voltage means sitting and waiting longer for it to open.

I intend to use something like this for remote for activation... http://www.amazon.com/Gikfun-Channel-Wireless-Control-Arduino/dp/B00Q9YBQC2/ref=sr_1_5?ie=UTF8&qid=1444413308&sr=8-5&keywords=arduino+remote

Get a driver that can do the work in the first place. 36V is too large to drive a simple MOSFET bridge, 12V its doable, any other voltage and you might as well build or buy a proper MOSFET bridge in the first place.

Pololu will have some suitable drivers - make sure they can handle peak stall currents and are rated at more than 40V if you need to run at 36. If you can run at a lower voltage (slower motor though) there will be more choices. The stall current will be less too.

However note that if you are driving a gate you need to have a foolproof safety system that prevents the risk of crushing - its best to ensure the operating force is too low to do damage, that's a failsafe way to ensure safety. The risk model is a small child or animal - think seriously about this.

Mark, thanks for the quick response. Running at 24vdc will mean 30% slower, but I may live with that, I will see what I can find pre-built as I am not up to designing my own. But as mentioned, I am comfortable soldering a kit or can breadboard from a schematic.

The safety risk, is pretty much zero. We live way out in the boonies and if anyone is likely to get caught in the gate, they would be at greater risk of rattle snakes, black-bear or Mountain Lion. I don't think bobcats attack, although a loose toddler a mile from the house might look like a nice snack. :D

I built an H-bridge using these logic level mosfets. These are rated for 60V/30A. SEE REPLY#6 DIY H-BRIDGE

I used these heatsinks ($0.40/EA) (drilled and tapped M3 thread)

Logic Level Mosfets

Thanks raschemmel, but I think I am on to something really cheap. Did some thinking and the analogWrite(pin,value) can be used to send a fixed output voltage between 0 and 5v. The output level is rated from 0 to 255. Divide that by 5v (255 / 5 = 51) so 51 steps per volt.

Here’s a rough and dirty that outputs the commented section and with a multimeter attached will control step up through 5-volts. That is a standard control voltage for a lot of manual PWM speed controllers. So off to Amazon and found a 60vdc x 15A controller for ten-bucks. I will use a 12v to 36v Boost and bingo - I hope. :slight_smile:

void setup() 
{ Serial.begin(9600);
  pinMode(10,OUTPUT);
}

float ctrA = 0;

void loop() 
{ ++ctrA;
  if ((int)ctrA <= 255)
  { Serial.print(ctrA,0);
    Serial.print("  ");
    Serial.println((ctrA / 51),2);
    analogWrite(10,ctrA);
    delay(100);
  }else
  { ctrA = 0;
  }
}
/*  Here is some of the output that matches the Multimeter readings.
Ctr  Voltage
1  0.02
2  0.04
3  0.06
4  0.08
5  0.10
6  0.12
7  0.14
8  0.16
9  0.18
10  0.20
11  0.22
...
...
...
93  1.82
94  1.84
95  1.86
96  1.88
97  1.90
98  1.92
99  1.94
100  1.96
101  1.98
102  2.00
103  2.02
104  2.04
105  2.06
106  2.08
107  2.10
...
...
...
245  4.80
246  4.82
247  4.84
248  4.86
249  4.88
250  4.90
251  4.92
252  4.94
253  4.96
254  4.98
255  5.00
1  0.02
2  0.04
3  0.06
4  0.08
5  0.10
6  0.12
7  0.14
8  0.16
9  0.18
10  0.20
11  0.22
*/

This is interesting too.

https://www.youtube.com/watch?v=IjgvKJrAOS4

The simplest solution would be just to use a relay and achieve the soft start by mounting the actuator on rubber bushes. It is usual to monitor the motor current to provide safety cut out and to stop the motor at the movement limits.

Russell.

russellz: The simplest solution would be just to use a relay and achieve the soft start by mounting the actuator on rubber bushes.

I don't think you understand the Inertia a 16-foot steel gate has when opening and closing. Rubber bushes would be crushed to pieces in a week.

Reducing motor speed is the only practical and sensible approach.

That is a standard control voltage for a lot of manual PWM speed controllers. So off to Amazon and found a 60vdc x 15A controller for ten-bucks. I will use a 12v to 36v Boost and bingo

Unless you have experience doing this (which somehow I would doubt or why would you be posting) or you are making a lot of assumptions. You didn't post any links for the hardware you plan to use. You might want to rethink that because the boost converter may not be rated for that load. We also don't have any information about the mechanical system. Normally, the way it works here is when there is some aspect of a project that cannot be conveyed with web links , a photo is posted (like one of the actual gate mechanical system) so the unknown part of the system can be evaluated. You are asking experts to make informed decisions with no information on the mechanical system and no photo of it. I agree with you about electronic softstart is preferable to some mechanical dampening scheme, however I think you should consult us about the hardware you choose (unless you have more electronics experience than you are disclosing)

If you dropped the operating voltage down to 24v, you might be able to use an h-bridge like below. The dish actuator might not last long trying to move your gate.

http://www.ebay.com/itm/Semiconductor-BTS7960B-43A-Stepper-Motor-Driver-H-Bridge-Drive-For-Arduino-YUUS-/161807192765?hash=item25ac75d2bd

WaitSome:
I don’t think you understand the Inertia a 16-foot steel gate has when opening and closing. Rubber bushes would be crushed to pieces in a week.

Reducing motor speed is the only practical and sensible approach.

Did you add 4 feet to the gate. It used to be 12.

I think russells is right. Motor current is a good indicator.
My satelite dish actuator uses it, and so do antenna rotators, and garage doors.

Use a relay for forward/reverse, and a single mosfet for switching.
The relay contacts might also be used for motor braking.
Leo…

What's your basis for comparing a rotating dish driver with a linear gate opener ?

They both have motors and move things. And OP is using a lineair actuator of an old satelite dish.

The gate/dish-mount/rotator/door has to be mechanically strong enought to withstand the power of the motor if when the system fails. A current sensor and a slow blow fuse are wise additions anyway.

A simple reed switch and magnet at both ends of the gate might be good. Detect the last inch, and PWM the mosfet there. End switches are needed anyway. The Arduino has to know if the gate is open or closed e.g. after a restart. Leo..

36V @ 5A is 180 W. The DIY H-bridge I built with mosfets from Sparkfun was rated at 1800 Watts but I guess if he isn't into DIY then ebay is the best solution.

A 2-relay board and a mosfet (or two in parallel) will cost you $5.00 and will do the same thing.

Unless you want the 16-foot gate to open/close ten times a second. Leo..

WaitSome: I don't think you understand the Inertia a 16-foot steel gate has when opening and closing. Rubber bushes would be crushed to pieces in a week. Reducing motor speed is the only practical and sensible approach.

That is what the gate at my work does. it is a real annoyance as it is set to operate about three feet out, rather than six inches which would be more than sufficient. End stops set by (large) reed switch units.

Wawa: And OP is using a linear actuator of an old satellite dish.

The gate/dish-mount/rotator/door has to be mechanically strong enough to withstand the power of the motor if when the system fails.

I begin to wonder whether a satellite dish actuator is sufficiently rugged to repetitively operate a gate. (OK, of course I have a couple here somewhere, just ready for when I get around to using them for something ...)

Wawa: End switches are needed anyway. The Arduino has to know if the gate is open or closed e.g. after a restart.

Absolutely!

WaitSome: I don't think you understand the Inertia a 16-foot steel gate has when opening and closing. Rubber bushes would be crushed to pieces in a week.

Reducing motor speed is the only practical and sensible approach.

Nonsense, have you looked at the bushes use on suspension links on vehicles? http://silentblocks.com/

Russell.

Rubber bushes

I believe you mean BUSHINGS

Wawa: End switches are needed anyway. The Arduino has to know if the gate is open or closed e.g. after a restart.

The commercial unit operating my gates just monitors the motor current. If it tries to close the gates when they are already closed the high motor current tells it that they are in the closed position so it opens them instead. No limit switches are used.

Russell.

The commercial unit operating my gates just monitors the motor current. If it tries to close the gates when they are already closed the high motor current tells it that they are in the closed position so it opens them instead. No limit switches are used.

Do you know what method is used to obtain current feedback ? (shunt ?)