Category: Uncategorised

High Temperature Paint

Needed something to protect the metal frames of the kiln I’m building from rust.

High Temperature paint is pretty easy to get a hold of. Found roughly 3 ranges: 300 °C, 500°C and 1000°C. The 1000°C range needs to be baked in an oven at 200°C to go hard.

Name Temperature Range Supplier
VHT Very High Temperature 704-1093 AutoBarn,Repco
VHT High Temperature 343 AutoBarn,Repco
Dupli-Color High Heat 1093 SuperCheap, Repco, Caswell, Autobarn
Whight Knight Hi Temp 540 Bunnings
Dulux Dura Max High Heat 300-690 Bunnings
Rustoleum High Heat 650 Ebay
Hammerite High Heat 600 Tenaru
Armor High Heat 650 Automegastore

 

Ebay MAX31855 not working

While writing the software for my wife’s new kiln I encountered a blocker. The MAX31855 module I got off Ebay wasn’t cooperating.

The SPI coms worked fine but the values received as cold (internal) temperature and probe temperature looked like they were random. Ordered 2 and they were both duds. Thought it might be a 5v vs 3.3v issue on the data lines so used a resistor divider network on he Scl and Sd lines on the second module just in case I damaged the first. The culprit unit:

Then ordered another 2 from a different supplier. This time the chip kept on replying with a short to ground. After some investigation the probe negative line was shorted to ground by an intentional track to ground on the PCB. Cut that track to break the connection and voila, error gone.

Last challenge was to get a stable reading. Turns out a 10nF ceramic cap across the thermocouple at the connection to the PCB was good enough. The values were alternating from 15 to 32 degrees before the modification. After the change it was a stable 24 degrees.

Lessons learned:

  • Test components received from Ebay before giving feedback.
  • The optional cap recommended to reduce noise, is not optional.
  • Only trust the OEM parts for fancy features like dual voltage support?

 

Usefull Youtubers

Category Channel Comment
Welding ChuckE2009 Knows his stuff. Good info on various types of rods and videos of welding puddle showing techniques.
Metal Machine Shop ThatLazyMachinist Knows his stuff (and he should as an ex-teacher). Machine shop lessons and various metal working projects.
Metal Machine Shop Mrpete222/Tubal Cain Editor of some of the ever popular Workshop Practice Series books.
Metal Machine Shop This Old Tony Unique presentation skills of various tips and projects.
Metal Gadget Prototyping Dan Gelbart Some really good techniques on achieving precision and prototyping.
Woodworking Matthias Wandel King of wood gears. Makes machines and stuff out of wood.