Enhanced K40 Temperature Monitoring

Updated K40 Temperature Sensing

I have one point of temperature monitoring  in my K40, water. I recently moved my K40 to the garage shop and decided to get rid of all the hacks and partially complete conversions. Temperature monitoring was one of those on the agenda to be completed. Mostly the temperature controller needed to be remounted but while I was at it I decided to add some more gauges .....

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For other information on the K40-S build use the  K40-S BUILD INDEX with schematics

More Temperature Monitoring

I already had a sensor in the water bucket connected to a controller that I had mounted lazily on the frame of the K40's kart.

This controller will alarm at an over temperature and since its relay is in the K40's interlock circuit it will shut off the laser.

This is the controller.  If its no longer available check for other similar ones. It needs to have an alarm function that opens the interlock when the temp setpoint it exceeded.

Gauge Mounting

The current controller/gauges were mounted on the upper part of the K40 control panel. It would have been nice if all these gauges were the same type. Then again their difference in appearance makes their varying purpose more obvious. In any case I went with function and cost over aesthetics.

One of my next projects will be to engrave acrylic labels for these. In the mean time their functions are:

• Upper left: Cabinet temp
• Upper right: Coolant temp
• Lower left: Laser tube temp
• Lower right: Laser power level

Gauge Installation

After removing the current control panel and then the hinged cover I used my nibbler to cut the holes for the new gauges. That nibbler is a must have "maker" tool!

Cabinet Temperature

This sensor is more of an experiment than anything. The sensor is located on the gantry near the air assist nozzle and is wired into the K40 interlock circuit. Its purpose it to sense a fire in the cabinet and turn the laser off. I have no way of testing or proving if this will work but I figured considering the damage a fire can do it was worth the effort and money! The idea is that a fire will melt the sensor and open the circuit. The controller will alarm if the sensor is disconnected and open the interlock circuit..... I hope.

I can imagine many cases where this may not work:

• The head is not near the fire
• The sensor shorts from the fire
• The cabinet self destructs before the sensor sees it

I used this 2 stage controller which is overkill but can be used if I ever build in a water cooler. 

I plan to set this alarm on this sensor to the lowest practical operating temperature I can.

Laser Tube Temperature

A sensor was tie wrapped to the laser tube's glass and routed to the gauge. This sensor monitors only and is not wired into the K40 interlock circuit. I hope to learn more about the temperature in the lasers cabinet and eventually plan to add air to that cavity. This gauge required a spacer since the panel sheet metal was to thin for the mounting tabs to firmly hold the meter in place.

As an FYI you can see the new water sensor and air assist connections at the bottom of the photo.

Laser Power Meter

The last meter in this set is the digital voltmeter that is connected to the LPS's control pot. I had to add a frame and filter to the naked small digital voltmeter so that it had a better mounting, is more readable and somewhat nicer looking.

I added gel filter material between the display and the face plate to get the display to be more readable.

Old Power Setting Meter ... dangling

Mounting and Wiring

Meter mounting. Note the adapters on the upper meters.

Enjoy, comments and suggestions expected :)

Don