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Labjack UE9 to Control a switch to a magnetic brake

control switch thyristor pnp

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#1 lan1990

lan1990
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Posted 28 July 2014 - 06:56 PM

Hi,

I am very new to electronics and the forums.Here goes my question:

I have labjack UE9 attached to encoders that read the position of the encoder.My matlab code works fine and keeps reading the pulses from the timers.

Now based on a particular value I need to switch a magnetic brake on and off.In other words I need to switch/break the power supply to the brake.

Attached links and pics of the brake below.

 

https://www.youtube....h?v=HrQPAZXsP6I

 

Basically it has 2 wires(+ve and -ve terminals).

How to I go about it?Shoud I use a PNP transistor?A switch maybe?If so ,How do i send a pulse from the labjack to the switch(i mean which code in matlab does that and does a 5v supply to the swich suffice)?

 

Thank you so much in advance.

Any help will be greatly appreciated.

Attached Thumbnails

  • brake imp.PNG


#2 LabJack Support

LabJack Support
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Posted 29 July 2014 - 12:41 PM

As per your video, your goal is to switch on and off a 24V supply to control the electro magnetic break.  You will need an external 24V power supply much like the one in the video that will remain powered on while you intend to control it.  Next, we usually recommend that you bet either a solid state relay or a mechanical relay compatible with 0-3.3V control logic that can control the 24V signal and provide the break with enough current.  Please check out the appnote that we have titled "controlling relays"
 
The type of solid state relay that we find our selves using most often for applications like yours is linked below:
 
You can also wire up your own circuit with PNP transistors but we usually find just buying a solid relay is a faster and simpler option.


#3 LabJack Support

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Posted 29 July 2014 - 12:55 PM

Hello,

 

The video on Youtube mentions a 24V power supply, and 300mA draw from the brake, so I'd recommend using either a PS12DC, or a relay + LJTick-RelayDriver to switch power. 

Comments:

PS12DC ($6.58 per channel)

  • Up to 12 channels
  • Limited to 750mA for 12 channels, or 1.5A for 6 channels
  • Do not have to purchase 3rd party relay module(s)
  • Directly connects to UE9 digital I/O lines (EIO/CIO)
  • Might require $3 added inrush current limiter as described in Figure 3, if the magnetic brake is a high inductive load (like a large DC motor).  You can determine if you need an ICL based on the armature resistance of the electromagnetic brake.  If armature resistance is >1.5-3Ω then you don't need an ICL

RelayDriver ($15.95 per channel, if you use KF0604D)

  • 2 channels per RelayDriver
  • Current limit is dictated by the relay
  • Directly connects to UE9 digital I/O lines (FIO/EIO etc)
  • Digital I/O logic is reversed using RelayDriver (Logic output low would turn the relay ON)
  • Must purchase 3rd party relay module, something like the KF0604D would work for 24V, or this one if your brake's DC voltage is much higher

If you try to use an PNP or NPN transistor, or build your own setup there are a lot of factors to consider.  The foremost consideration is that if you do anything wrong, you could easily damage the UE9 because 24V is too high voltage for the digital I/O of the device.  The PS12DC is optically isolated from the UE9, thus eliminating this risk.  The RelayDriver module is not isolated from the UE9, but the KF0604D(or any other solid-state relay) provides isolation.

 

Which code in matlab?  Use any of the digital I/O example code.

 

Here is a related app-note on the subject of controlling relays: http://labjack.com/s...trolling-relays




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