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18x18 Monster Heatbed doesn't turn off

K

konton

Member
#1
#1
So after a week of tests with a small heat bed, I finally got a SSR-50 DA Solid State Relay to connect my 18x18 Monster Heatbed to my Gmax for temp control. When powered up in testing everything is fine. But once the heatbed gets to the right temp, it goesn't shut off. I can see the flashing lights on the RAMPS and the Relay in prep to shut-off. But the heatbed continues to get hotter.

Researching it seems I may need something like a bleeder resistor to keep current leakage that prevents the heat bed from turning off. Can any help me which knowing what exactly I need to purchase? Thanks!

Justin
 
R

raykholo

Member
#4
#4
I believe 1/4 watt is standard, but anything higher won't be a problem. The link should be fine.

By standard I mean the overall observation of what you would find on an electronics bench in the context of arduino and microcontrollers.
 
R

raykholo

Member
#6
#6
I googled "ssr bleeder resistor".

From the results on the first page, I'm seeing a few things: The resistor is placed in parallel with the load. So the 2 wires going to the bed, the resistor is hooked up to the same contacts.

Test with the ones you linked, it's not dangerous if they burn out, but then you'll know that you need a higher wattage resistor. I don't think you will.
 
R

raykholo

Member
#8
#8
I've always found that the people who aren't as electrically inclined make the best diagrams. :)

The diagram makes sense, I'm just confused now. I believe the resistor should go between 1 and 2 of the ssr (red and blue wires) but that could also not be it. Play around a bit, let me know what you come up with.
 
K

konton

Member
#13
#13
Okay. Well going back to the transistor, any ideas? I'm talking to Jim, the guy who builds them. He said they don't ever need a transistor and do not use a mechanical relay. So what specifics should I ask hum to know the specifics of a transistor I should be using?
 
R

raykholo

Member
#14
#14
The transistor has to do with the fact that arduino can't provide enough current to activate the relay on its own. So the transistor (or MOSFET) is used as an intermediate between the board and relay. For general applications, I use 2N3904 they are pretty common. The RAMPS board uses a stp55nf06l Mosfet.
 
K

konton

Member
#15
#15
Hmmm. . . . seems like I should take a real world approach to this. I assumed that I could just test this using the connectors to the extruders. But it might be better to connect it to where the headbed would actually be controlled from.

That being said I need to update the Dual Extruder Marlin to display the heatbed temp on the LCD. Any ideas Ray? As I recall you don't have an LCD.
 
R

raykholo

Member
#16
#16
Got an LCD this morning with my shipment of Arduinos, Ramps board, stepper drivers, and hotend heaters/ thermistors. Talk about good timing...

Quite a bit finicky to setup, took a while to get everything working. A lot of static sensitivity. The knob won't control the menu, but it does work, so it might be firmware related. Don't really care enough at the moment to test.

If you have dual extruders, use the 3rd of those terminals to test your relay. Disconnect the cooling fan for the time being. You can always rig this up later for the fan: http://www.geeetech.com/wiki/index.php/Reprap_Ramps1.4_RRD_Fan_Extender

Everything you need to change in the firmware should be in the Configuration.h file.

Don't forget the diode! (I'm just teasing)
.
Add: But if you use repetier on the computer, it'll tell you all the temps in the manual control tab.
 
K

konton

Member
#17
#17
Sorry. I got sidetracked trying to build a mini kossel that used magnets. I'm not sure why. I just like magnets. And I have 36 wheels for misumi 1515 t-slots. so . . . .

I also have a Fan Splitter sitting around from another pointless purchase:
http://gadgets3d.com/index.php?route=pr ... duct_id=89

Not sure where to connect it. I assume this will also work?

My knob works. Have you tried different LCD's? I assume you got a couple? Did you also buy from open builds yet. I want to, once I get that miter saw which I have no space for.

Justin
 
R

raykholo

Member
#18
#18
I bought so much OpenBuilds inventory that I became a distributor. Let me know if you need anything.
I've warmed up to the idea of a Delta. I want one now... The print speeds would be so fast.... All in due time...

I also spent $130 on nuts and bolts.

The first thing I'm doing right now is an automated fence for my miter saw. Just punch in the desired cut length and slide your stock to till it hits the fence-wall. Check out TigerStop.

I only bought the one LCD shield, but I do have "plain" 16x2 character LCDs for other projects.

Reference that other fan splitter link for the pin.
 
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