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Controlling linear actuator from microcontroller

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ErikY:
I am playing around with different actuators for a project I have in mind, and I bought a high speed linear actuator.

This has a positive and a negative wire only, and no data connection wire.

Much like a DC motor.

Originally, I was thinking I could run this like a motor using an h-bridge, in particular the SN754410, on my $50 robot board that I have, which is Webbot's version using the 6v and the 9V battery sources, one for the motors and one for the mcu.

Then I realized that the linear actuator needs 12 volts, not the ~6 usually required for a DC motor, and it can require up to 9 amps.

So, I don't think I can use the SN754410 nor the $50 robot board.

So I was going to make anew board, kind of a spinoff of the $50 robot board, but using the 328P instead of the ATmega8, and with a 12V battery source (2 6V in series) for running the linear actuator.

What I am wondering is if I can run the red linear actuator wire to a 12V power source, and the black linear actuator wire to a i/o pin on the mcu, so that when the pin goes low, it is connected, and when the pin goes high it is disconnected.

My hope is that since the power is coming from the 12V batteries, and not the mcu, I will not fry my circuits.

Would this work?

If not, can anyone help me out with how I can do this?

Soeren:
Hi,


--- Quote from: ErikY on August 08, 2012, 01:45:18 PM ---This has a positive and a negative wire only, and no data connection wire.

Much like a DC motor.

--- End quote ---

It is a DC motor.

If it hasn't got end stop switches, you need to use over current detection to break the power when at either end.



--- Quote from: ErikY on August 08, 2012, 01:45:18 PM ---What I am wondering is if I can run the red linear actuator wire to a 12V power source, and the black linear actuator wire to a i/o pin on the mcu, so that when the pin goes low, it is connected, and when the pin goes high it is disconnected.

--- End quote ---

Let's pretend that you never suggested pulling 9A through an I/O pin ;)
Besides, even if it could handle the current (eg. by a transistor in-between), how about reversing direction?

Here is a cheap way to get both directions and not frying your controller in the process :)  http://That.Homepage.dk/PDF/PWM+Relay_4_Motor_Ctrl.pdf
The relay makes the equivalent of an H-bridge and the MOSFET makes it PWM
able (so that you can control the speed of it. If you don't need that, a relay (with a driver is all it takes - plus an over current detector if there's no end stop switches as mentioned (Now you wish you had included a link :P)

ErikY:

--- Quote from: Soeren on August 08, 2012, 04:27:49 PM ---Hi,


--- Quote from: ErikY on August 08, 2012, 01:45:18 PM ---This has a positive and a negative wire only, and no data connection wire.

Much like a DC motor.

--- End quote ---

It is a DC motor.

If it hasn't got end stop switches, you need to use over current detection to break the power when at either end.



--- Quote from: ErikY on August 08, 2012, 01:45:18 PM ---What I am wondering is if I can run the red linear actuator wire to a 12V power source, and the black linear actuator wire to a i/o pin on the mcu, so that when the pin goes low, it is connected, and when the pin goes high it is disconnected.

--- End quote ---

Let's pretend that you never suggested pulling 9A through an I/O pin ;)
Besides, even if it could handle the current (eg. by a transistor in-between), how about reversing direction?

Here is a cheap way to get both directions and not frying your controller in the process :)  http://That.Homepage.dk/PDF/PWM+Relay_4_Motor_Ctrl.pdf
The relay makes the equivalent of an H-bridge and the MOSFET makes it PWM
able (so that you can control the speed of it. If you don't need that, a relay (with a driver is all it takes - plus an over current detector if there's no end stop switches as mentioned (Now you wish you had included a link :P)

--- End quote ---


Soeren,

Thanks much for your reply!

OK, I spent a lot of time trying to understand the circuit you showed me.

First off, the linear actuator does have built in limit switches, so that is a plus.


I have a few  questions that I just don't understand and cannot figure out.

Is SV1 what connects to my mcu?

I am assuming the V+ and V- are dedicated 12V from a battery source?

There is also a circle with a rectangle around connecting to transistor bd140, what is that?

Also, the 4 circles on the corners of the silksreen, are those for mounting the board?

For the DPDT relay, what is the 351 representing?

I THINK that is it for now, I think I get the rest of it.

Once again, thanks!





Soeren:
Hi,


--- Quote from: ErikY on August 09, 2012, 07:55:59 AM ---First off, the linear actuator does have built in limit switches, so that is a plus.

--- End quote ---
Yes, you can feed them to I/O lines w. pull-up either internal or physical resistors from the I/O to Vdd (+5V or whatever you use). The other end of the switch should go to ground (twisting the wires going to each switch around 3 times per inch will make it more immune to motor noise). You could feed both switches to a single line, if your pin "budget" is tight and then keep track of direction in software (assuming you either extend or retract it completely on power up, to know where it is).



--- Quote from: ErikY on August 09, 2012, 07:55:59 AM ---Is SV1 what connects to my mcu?

--- End quote ---
Yes, the layout is made for "Berg pins" (the pin rows w. square pins that's used in almost all controller boards) - soldered wires would work if needed.



--- Quote from: ErikY on August 09, 2012, 07:55:59 AM ---I am assuming the V+ and V- are dedicated 12V from a battery source?

--- End quote ---
There's no V-, but you probably mean the 0V and if so, yes, and the relay should be 12V as well.



--- Quote from: ErikY on August 09, 2012, 07:55:59 AM ---There is also a circle with a rectangle around connecting to transistor bd140, what is that?

--- End quote ---
Assuming you mean on the overlay (I stared at the schematics for a couple of minutes and didn't know what you were on about ???) - it's the BD140 itself. It's because of the symbol I used was for a transistor bend down flat on the board and the circle is the "no-go" area, had it been inside the copper pour, but it should be mounted standing up.



--- Quote from: ErikY on August 09, 2012, 07:55:59 AM ---Also, the 4 circles on the corners of the silksreen, are those for mounting the board?

--- End quote ---
Yes.



--- Quote from: ErikY on August 09, 2012, 07:55:59 AM ---For the DPDT relay, what is the 351 representing?

--- End quote ---
It's just the relay symbol I used (a relay called 351). If you intend to make a PCB, wait until you have a suitable relay (they come in all sorts of pinouts), then, if it doesn't fit the one I used, give me a link to a datasheet containing the physical measures of it (and it's pinning) and I can modify the layout to suit.

If you can't find a DPDT relay that can handle the needed current, two SPDT or DPST can be used instead.

For larger currents, automotive relays are quite cheap compared to their current handling capacity.

ErikY:

--- Quote from: Soeren on August 10, 2012, 07:24:39 PM ---Hi,


--- Quote from: ErikY on August 09, 2012, 07:55:59 AM ---First off, the linear actuator does have built in limit switches, so that is a plus.

--- End quote ---
Yes, you can feed them to I/O lines w. pull-up either internal or physical resistors from the I/O to Vdd (+5V or whatever you use). The other end of the switch should go to ground (twisting the wires going to each switch around 3 times per inch will make it more immune to motor noise). You could feed both switches to a single line, if your pin "budget" is tight and then keep track of direction in software (assuming you either extend or retract it completely on power up, to know where it is).



--- Quote from: ErikY on August 09, 2012, 07:55:59 AM ---Is SV1 what connects to my mcu?

--- End quote ---
Yes, the layout is made for "Berg pins" (the pin rows w. square pins that's used in almost all controller boards) - soldered wires would work if needed.



--- Quote from: ErikY on August 09, 2012, 07:55:59 AM ---I am assuming the V+ and V- are dedicated 12V from a battery source?

--- End quote ---
There's no V-, but you probably mean the 0V and if so, yes, and the relay should be 12V as well.



--- Quote from: ErikY on August 09, 2012, 07:55:59 AM ---There is also a circle with a rectangle around connecting to transistor bd140, what is that?

--- End quote ---
Assuming you mean on the overlay (I stared at the schematics for a couple of minutes and didn't know what you were on about ???) - it's the BD140 itself. It's because of the symbol I used was for a transistor bend down flat on the board and the circle is the "no-go" area, had it been inside the copper pour, but it should be mounted standing up.



--- Quote from: ErikY on August 09, 2012, 07:55:59 AM ---Also, the 4 circles on the corners of the silksreen, are those for mounting the board?

--- End quote ---
Yes.



--- Quote from: ErikY on August 09, 2012, 07:55:59 AM ---For the DPDT relay, what is the 351 representing?

--- End quote ---
It's just the relay symbol I used (a relay called 351). If you intend to make a PCB, wait until you have a suitable relay (they come in all sorts of pinouts), then, if it doesn't fit the one I used, give me a link to a datasheet containing the physical measures of it (and it's pinning) and I can modify the layout to suit.

If you can't find a DPDT relay that can handle the needed current, two SPDT or DPST can be used instead.

For larger currents, automotive relays are quite cheap compared to their current handling capacity.

--- End quote ---

Soeren, Thank you much for your help! Much appreciated!

I am going to order some parts and try this out.

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