New guy with a simple question

abcgmeier · Apr 24, 2011

Need some help please; I am new to the forum and possibly a little ignorant.
I need to use a relay to run a 12 DC actuator; the polarity needs to change to move it in and out of course.
My issue is the control for the actuator only provides a single input for the relay coils but reverses the polarity to drive a lower amp actuator directly using its built in relays.
So I need to energize the relays that drive the actuator based on the polarity applied to the coils.
12 vdc 15 amp load
Example using two relays
Relay 1 energizes when wire 1 is positive and wire 2 is negative. (Drives the actuater in)
Relay 2 energizes when wire 1 is negative and wire two is positive. Drive the actuator out
I was looking at latching relays but I need the actuator to stop when the coil is de-energized. My understanding is they do not.
Any ideas?

milldrone · Apr 24, 2011

abcgmeier said:
My issue is the control for the actuator only provides a single input for the relay coils but reverses the polarity to drive a lower amp actuator directly using its built in relays.

If I'm understanding your request correctly, you want a "H bridge".
http://en.wikipedia.org/wiki/H_bridge

In the pic I posted, imagine your polarity sensitive controller in place of the "M"

leitmotif · Apr 25, 2011

What Vaugn has drawn for you is the standard reversing setup when line voltage is always the same and never changes polarity.

However you seem to indicate the power supply changes the polarity of the line to reverse the motor. Is this true?
IF so you do not need reversing contacts or multiple relays.
You may need only one relay to disconnect from power supply to give the power supply time to reverse polarity and - maybe more important - to let the motor come to a stop before energizing it in opposite direction.

Dan Bentler

abcgmeier · Apr 25, 2011

Sorry if I am confusing the issue. I have a circuit board that controls a small DC actuator at 3 amps. It moves the actuator in and out by reversing the polarity on the two wires that lead to the actuator. It does this using two board mounted relays. This leaves me with the need to add another relay to handle a new 15 amp actuator between the board and the actuator, but the only thing I have to tell me to extend or contract the actuator is the two leads from the board that change polarity, but can only handle 3 amps.
This all done at 12 volts

todster · Apr 25, 2011

Check out some polarized relays. http://www.secutron.com/./media/datasheets/CAT-5012_PAM_Series_Multi-Voltage_Relay_Modules.pdf These are only 10 amp but it will give you the idea of what to look for in a higher current rating.
You could also try 2 automotive type relays with maybe (2) 1N4001 in series and inverted.
Any chance of taking the inputs to the relays on the C-B and rum them to heavier relays instead?

abcgmeier · Apr 25, 2011

Attached is an idea I have. I do want to change the CB relays because I am going to be doing some other work that will need this set up.

bernie_carlton · Apr 25, 2011

Shamelessly stealing and modifying Vaughn's excellent diagram, this is my illustration of Todster's suggestion. Y0 and Y1 being the ouputs from the interface board which currently exists.

abcgmeier · Apr 25, 2011

Thanks, I believe I can make this work next question.
If I want to slow down the actuator speed but keep it adjustable do I just use a potentiometer before the relay contacts.

bernie_carlton · Apr 25, 2011

You hadn't mentioned anything about adjustable speed before. That may change everything. Can you provide a link to this actuator control board?

jrwb4gbm · Apr 25, 2011

Here are my ideas on this project, shamelessly borrowing Vaughn's and Bernie's drawings and ideas. I could be wrong about what is the final task, so, if this doesn't help, just disregard. At 15 amps I believe an Adjustable Voltage Power Supply will work better than just a large potentiometer before the relay contacts.

abcgmeier · Apr 25, 2011

Ok, here is all of what I am doing. I am working on changing some of my solar panels into a tracker that moves with the sun. I want to make this something that my son and I can do together. The CB I have is a kit that uses photo resistors to track the sun and drive an actuator. Attached is the schematic for the kit, it is still in pieces waiting to be assembled. So I can change the relays, but I do not know what relays to use with the same pin foot print. I did miss read my amp requirements I have a 4.73 load at 12 volt DC. This is still more than the Axicom V23105-A5003-A201 is rated for.
Besides the board I am planning on adding some more features. I have wind activated switch spdt that I want to use to drive the panels to 0 degrees; this will protect them on high wind days. I am planning on using a two tilt switches operating opposite of each other to drive the actuator when the wind is high. I do not think I can trick this board to this so I was going to use relays to remove the board from the circuit and let the tilt switches take over until the wind dies down. So I was thinking that since I need relays to switch between the CB and the wind circuit I would not worry about the board relays.
I also want to add speed control to the actuator since tracking the sun need slow movements.
For my son I would like to try and build a circuit board from scratch to handle the added requirements, but the layout is kind of out of my experience. I understand the diodes so that is simple.

milldrone · Apr 26, 2011

bernie_carlton said:
You hadn't mentioned anything about adjustable speed before. That may change everything.

abcgmeier said:
Ok, here is all of what I am doing. I am working on changing some of my solar panels into a tracker that moves with the sun.

abcgmeier,

Here is a link to another PLCs.net thread concerning solar tracking, and what to do if it's cloudy.

http://www.plctalk.net/qanda/showthread.php?t=55817&highlight=solar

New guy with a simple question

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