Connecting a linear actuator (linak) to a dimmer

AAH

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For moving props it's sometimes desirable to use a linear actuator to move a prop up/down, in/out etc. The term linear actuator is often shortened to Linak but this is actually a brand name.
The wiring diagrams attached are for a linear actuator that has built in end switches. ie when you power them and they get to the end of the stroke they have a switch internal to them that cuts off power.
When controlling relays the output of the DC dimmer must be controlled with a 0% or 100% signal with no global dimming in effect via an E1.31 board or the sequencer.
The 2 relay control method allows the linear actuator to be moved part of the stroke controlled by how long the output is turned on for. The outputs would be labelled as extend and retract or up and down or similar. Turning off the extend or retract output will leave the actuator where it is.
The single relay control method only allows a fully extended or fully retracted control. As soon as power is supplied via turning on the output the actuator will start moving and will continue moving until it hits the end of it's stroke or power is turned off via turning off the output. As soon as power is removed from the output the actuator will retract until it reached the end of it's stroke.
The 1N4004 diodes are required to prevent the back EMF (coil spike) from damaging the mosfet output transistor/s of the dimmer.
The extend or retract can be swapped by changing the 2 wires going to the actuator.
The same power supply can be powering the dimmer pcb as the actuator or alternately a different power supply could be used.
The relay needs to be the same voltage as whatever is powering the dimmer pcb.
The fuse should be sized to suit the actuator.
 

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stevelee

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I’m setting my first year goal to include a Boscoyo Santa Riding Motorcycle and use a linear actuator to get it to do a wheelie.

Would it be possible to control a dmx relay board from the rPI-28+ ?

I’ll most likely use 2 outputs (one for extend and one for retract) and use them to switch a dual pole relay so that there’s only power on the actuator when I want it to move.

Thanks
Steve
 

Kurt87

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Might be worth mentioning that in this set-up where you are switching both + and - poles via the same relay it’s important to make sure that the relay is a “break before make” type as not to momentarily cause a short
 

stevelee

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Might be worth mentioning that in this set-up where you are switching both + and - poles via the same relay it’s important to make sure that the relay is a “break before make” type as not to momentarily cause a short
I was going to have the the extend relay switch both + and - and the retract relay switch both + and - independently of each other. That way there’s only ever power on the actuator when I want it to move
 

David_AVD

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Here's a circuit I drew up for running a reversable motor from 2 drive lines.

You can ignore the resistors and transistors and just use the relay section.

One line makes it go one way, the other line makes it go the other way.

If both relays are on or off the motor is stopped.
 

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stevelee

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That relay method is a very bad idea. What happens when both are on? (BOOM)
Unless there a programming fault, or controller fault, welded contact etc both relays shouldn’t be on at the same time.

ELV goes pop
LV goes bang
HV goes boom
 

TerryK

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For something like this there is typically a hard interlock contact wired in too with whatever else is driving the direction contactors/relays.
 

BAZMick

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Yes, electrical interlock where the relay 1 switch wire goes through an NC contact on relay 2 and vice versa for relay 2. So relay 1 can never turn on when relay 2 is on. This is how big industrial motors are started in start/Delta configuration.
 

stevelee

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I always put both mechanical and electrical interlocks in forward reverse motor starters and between the delta and star contractors
 

stevelee

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So back to the other part of my initial question, is it possible to use the dmx port in a rPI-28D+ to control a dmx relay output controller ?
 
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