Independent hot end control.

[JohnnyRobot]

Hey all,

I'm trying to do something crazy here. As the title suggests, I'm trying to make an independent V3B hot end control.

We are upgrading our 3D printing FANUC robot and I have been assigned to design the controls as quickly and as cheaply as possible. Here's a rough sketch of my idea...

The 9V battery is really just meant to be an illustration of a 24V power supply.



Any ideas?

[insta]

Get one of the all-in-one $35 PID controller kits off of eBay. Some of them have a relay inside that'll do 120v @ 10A, more than enough to run the hotend. They use an (included) thermocouple, too, and read them temperatures themselves.

http://www.ebay.com/itm/New-TA4-RNR-PID ... 3f40359751
http://www.ebay.com/itm/1PCS-K-Type-The ... 259d58c2dd

Tape the thermocouple to the heater block with Kapton and put the rubber boot back on. Power the PID controller with 120vac (be careful...). Connect the relay terminals of the PID controller inline with the hotend like a switch. Fire it all up, set it to autotune, be merry.

[ednisley]

Get one of the all-in-one $35 PID controller kits off of eBay.

Absolutely!

Buy the biggest blocks you can, wire 'em together, and don't putz around with circuit design & DIY Arduino sketches. This stuff is dirt-cheap on eBay / Amazon, so if your time is worth more than $0/hr, everybody comes out ahead.

a relay inside that'll do 120v @ 10A

Mechanical relays have both an AC rating and a DC rating. If you believe the eBay specs for that controller:

• 250V/3A AC
• 30V/3A DC

Usually, the AC current rating will be higher than the DC rating, because they use the zero crossings to extinguish the contact arc. In this case, they're the same, which puts an orange flag on the specs.

In any event, that's much much much less than you need for a heated build platform. Switching the platform through an outboard DC-DC (not the usual DC-AC) solid state relay would be a Very Good Idea, because it removes the mystery specs from the design:

http://www.ebay.com/itm/1pcs-Soild-Stat ... 0737814413

Whatever the 24 V platform current might be (one measurement trumps one kilo-opinion), get an SSR rated at twice that value.

The thermocouple attaches to that controller through screw terminals, not a Type K connector, so you must figure out the polarity on your own: if the temperature reading makes no sense, swap the connections. Better yet, get a sack of female Type K connectors:

http://www.ebay.com/itm/5X-New-Female-K ... 1508059056

Wire one up appropriately and you have a no-goof connection for standard thermocouples.

[insta]

Silly Ed, this is for the hotend, not the bed He's only pulling an amp or so at 24v, which the onboard relay will do just fine.

The current ratings being the same isn't unusual, that's the rating of the flex wire. The voltage difference is for arc extinguishing when switching under load.

[ednisley]

this is for the hotend, not the bed :)

Point taken... but, remember, nothing exceeds like excess.

the rating of the flex wire

That would be, what, 24 AWG?

Makes you afraid to look inside the controller, doesn't it?

[insta]

this is for the hotend, not the bed

Point taken... but, remember, nothing exceeds like excess.

the rating of the flex wire

That would be, what, 24 AWG?

Makes you afraid to look inside the controller, doesn't it?

Nah the flex wire inside the relay. The controllers themselves don't have any moving parts outside of that relay, not too much to fail assuming you listen to something resembling the ratings

[JohnnyRobot]

Thanks everybody. That is a great solution. If it were up to me, I'd use it.

After presenting the idea to the boss man, he still wants to go the Arduino route. The 3D printing robot is going to be featured at the Detroit Henry Ford Museum Maker Fair.

He wants to use an Arduino to show that the robot is capable of communicating with "Maker Friendly" hardware. So now I'm back at the drawing board.

[insta]

Take a page from the Steampunk guys and just stick Arduinos and Sparkfun components all over the PID controller

That's a stupid requirement he gave you