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Hotend Problems

Posted by BradStaff 
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BradStaff
Hotend Problems
May 14, 2014 11:15PM
What amount of voltage should I be getting for my hotend from my Ramps 1.4 board if I'm running Marlin? I'm about to order a new hotend or something. This is really frustrating. Any help?
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Cefiar
Re: Hotend Problems
May 15, 2014 03:07AM
If you're feeding the board 12V, then you should get very close to that across the hotend.

If you don't have a thermistor hooked up, or Marlin reads too low a temp on the thermistor, it will not turn the hotend on.

Note: Disconnected and very low temp are pretty much the same thing for a thermistor, which is why the software disables the output if it's "too low". If the thermistor breaks or a wire falls out, your hotend will continue to heat and never turn off when at temp, as the temp reading will still be sitting at the same value. This could result in the hotend getting damaged* and possibly taking the printer (and you) with it.

[*] - PTFE burning, PEEK burning, or in the case of an all-metal hot end, the mount bending, your carriage melting/falling off, or your aluminium heatblock melting. All are possible, depending on the type of hotend and/or type of heating element.
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BradStaff
Re: Hotend Problems
May 15, 2014 07:41PM
Quote
Cefiar
If you're feeding the board 12V, then you should get very close to that across the hotend.

If you don't have a thermistor hooked up, or Marlin reads too low a temp on the thermistor, it will not turn the hotend on.

Note: Disconnected and very low temp are pretty much the same thing for a thermistor, which is why the software disables the output if it's "too low". If the thermistor breaks or a wire falls out, your hotend will continue to heat and never turn off when at temp, as the temp reading will still be sitting at the same value. This could result in the hotend getting damaged* and possibly taking the printer (and you) with it.

[*] - PTFE burning, PEEK burning, or in the case of an all-metal hot end, the mount bending, your carriage melting/falling off, or your aluminium heatblock melting. All are possible, depending on the type of hotend and/or type of heating element.
So I'm getting about 20C from my thermistor. I set it to heat and....nothing. I check D8, D9, and D10 and am getting no voltage. Whats happening? Is it in the code? Short in my RAMPS board?
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vreihen
Re: Hotend Problems
May 15, 2014 09:35PM
Did you hook up the +12V power supply onto the 5A power input connector, or only to the heatbed 11A input?????
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BradStaff
Re: Hotend Problems
May 15, 2014 11:42PM
I've tried both and still gotten nothing. Which one should I use if I don't have a heated bed?
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waitaki
Re: Hotend Problems
May 16, 2014 03:59AM
You must use the outer of the 2 sockets. I assume you have checked there is indeed 12v on the connector? When you press the heater on button, does the heater LED on the Ramps illuminate?

_______________________________________
Waitaki 3D Printer
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vreihen
Re: Hotend Problems
May 16, 2014 07:18AM
+12V power for everything but the heated bed comes off of the 5A power rail:

http://reprap.org/wiki/RAMPS_1.4



As waitaki asked, did you check your +12V input power? The boards will happily run from USB power and appear to be live, but you will not have power to the stepper motors or hotend. Also, check the 5A power input connectors for signs of burning, which is another common problem.....
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BradStaff
Re: Hotend Problems
May 16, 2014 08:36AM
Ok. So I am getting 12V out of my power source. I am not seeing an LED light up. I think my RAMPS is burned out.
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cdru
Re: Hotend Problems
May 16, 2014 05:54PM
Measure the voltage between the D10 POSITIVE terminal and supply GROUND (NEGATIVE) from your power supply. You should always see 12v there even when the hot end is not being called for as long as the power supply is on. If you have 12v there, measure the voltage between the pin on the MOSFET furthest away from D10 and the supply ground. You should have close to 5 volts here when the hot end is being called for. If you have 5 volts but not 12v, then your mosfet(s) are fried. If you don't have 5 volts, your Arduino is either fried (less likely) or it's misconfigured (more likely, post your configuration.h file).
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BradStaff
Re: Hotend Problems
May 17, 2014 05:15PM
I'm getting no voltage on D10 POSITIVE to Power Supply Negative but I am getting it on D8 POSITIVE to Power Supply NEGATIVE. 12V. What does that mean?
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BradStaff
Re: Hotend Problems
May 17, 2014 08:36PM
I'm honestly about to just get a new RAMPS board. It's very likely burnt out because i remember one time when the hotend did work. I'd rather get a new one than to get all inside it to try and fix it and probably ruin it. Right?
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Dust
Re: Hotend Problems
May 18, 2014 08:44AM
D8 is a separate cct, the 11amp cct

sounds like your 5A fuse is gone, so 12v isnt getting to anywhere but the heated bed.
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BradStaff
Re: Hotend Problems
May 18, 2014 10:15AM
Well that sucks. Should I get a new RAMPS Board or can I fix it?
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jbernardis
Re: Hotend Problems
May 18, 2014 02:52PM
You can definitely repair it if it's the fuse. The fuses are the yellowish rectangular objects near the power connector. The smaller one is for 5A, the larger for 11A. You can test with a voltmeter between ground and each of the legs of the fuse. You should get 12V from both. If you only get it from 1, you know you have a bad fuse. They are large enough where they're easily de-soldered and a replacement soldered in. It should be a 5 minute job assuming you get the part. I'm not sure which one you'd need, but mouser has them for pennies.

Here is a search result form their site.
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BradStaff
Re: Hotend Problems
May 18, 2014 04:00PM
I'm not getting it from either of the legs of the smaller one when I'm going from my input negative to one of the legs. I was getting 12V on the other(larger) fuse. Does that seem correct?
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jbernardis
Re: Hotend Problems
May 18, 2014 04:55PM
Checking between ground (negative) and either leg of the fuse is the correct way to do it. There is absolutely nothing between the power supply connector and the fuse - so you should see 12 volts on at least one of them. If you're not seeing it on either, you either have a bad trace (fairly unlikely) a bad connector, or a bad power supply. Do you get voltage between the two power connectors for the 5 Amp rail?
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BradStaff
Re: Hotend Problems
May 18, 2014 05:55PM
Quote
jbernardis
Checking between ground (negative) and either leg of the fuse is the correct way to do it. There is absolutely nothing between the power supply connector and the fuse - so you should see 12 volts on at least one of them. If you're not seeing it on either, you either have a bad trace (fairly unlikely) a bad connector, or a bad power supply. Do you get voltage between the two power connectors for the 5 Amp rail?
Yes.
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BradStaff
Re: Hotend Problems
May 18, 2014 07:04PM
I'm about to order new fuses. What kind should I be getting?
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waitaki
Re: Hotend Problems
May 19, 2014 01:38AM
Pointless getting fuses if you have no voltage going to them (or rather it - the small one). Look under your Ramps and check if there is 12v between the two solder tabs that connect the 12v 5A socket.

_______________________________________
Waitaki 3D Printer
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BradStaff
Re: Hotend Problems
May 19, 2014 08:59AM
Yes I'm getting voltage going to the small one but it's not going through the fuse like we established earlier which means that I have to replace the fuse. Right?
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jbernardis
Re: Hotend Problems
May 19, 2014 02:51PM
Yes - but you said earlier that you weren't getting voltage on either leg of your fuse. So how are you getting voltage on the bottom of the board at the solder joint that does not show up on the leg that's connected there. If you ARE getting voltage there, but not on the other leg of the same fuse, then, yes, you most likely have a bad fuse. Check the link I gave you earlier - I think the first fuse on the page will meet your needs.
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cdru
Re: Hotend Problems
May 19, 2014 04:08PM
Quote
jbernardis
Check the link I gave you earlier - I think the first fuse on the page will meet your needs.
No. Your link is for 2.5 amp polyfuses. It should be a 5 amp polyfuse which means the 5 amps is the maximum current the fuse will pass without tripping. Typically but not always the trip current, or minimum current that is guaranteed to cause a trip, will be about twice the hold current.

The original specs called for a MFR500 fuse which will allow up to 5 amps to pass through all day long, start to warm over 5 amps and trip after a while, and quickly trip at 10 amps or more.
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BradStaff
Re: Hotend Problems
May 19, 2014 08:15PM
Ok. Change everything that's just happened. I've had it set up incorrectly. I misread something earlier. I've had it hooked into the rails on the left (11A) and not the one on the right (5A). After I switched it, I checked D10 and I got 12V from Power Input Negative to D10 Positive. I feel so stupid. I then checked Power Input Negative to the furthest mofset pin from D10 and got 12V. What happens now?
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waitaki
Re: Hotend Problems
May 19, 2014 10:27PM
In that state, the mosfet is not switched on. So, press the heater on button - does the LED come on or the heater work? If not, and with the heater still switched on, check the left most pin on the mosfet - does it read 5v or nothing?

_______________________________________
Waitaki 3D Printer
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BradStaff
Re: Hotend Problems
May 19, 2014 10:30PM
Quote
waitaki
In that state, the mosfet is not switched on. So, press the heater on button - does the LED come on or the heater work? If not, and with the heater still switched on, check the left most pin on the mosfet - does it read 5v or nothing?
It reads 12V.
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jbernardis
Re: Hotend Problems
May 20, 2014 01:02AM
Quote
cdru
Quote
jbernardis
Check the link I gave you earlier - I think the first fuse on the page will meet your needs.
No. Your link is for 2.5 amp polyfuses. It should be a 5 amp polyfuse which means the 5 amps is the maximum current the fuse will pass without tripping. Typically but not always the trip current, or minimum current that is guaranteed to cause a trip, will be about twice the hold current.

The original specs called for a MFR500 fuse which will allow up to 5 amps to pass through all day long, start to warm over 5 amps and trip after a while, and quickly trip at 10 amps or more.

Thanks for the info. I wasn't certain when I was searching, but I thought that the 5 amps I was looking for was the trip current. Now I know better.
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BradStaff
Re: Hotend Problems
May 20, 2014 06:36PM
No LED light when I switch the heater on. I'm getting nothing from Supply ground to D10's far left Mosfet pin. Arduino Problem? I've attached my Configuration.h file.

Configuration.h
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cdru
Re: Hotend Problems
May 21, 2014 08:17AM
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BradStaff
No LED light when I switch the heater on. I'm getting nothing from Supply ground to D10's far left Mosfet pin. Arduino Problem?
Presuming that you have the RAMPS board oriented so that the power connectors are on the left edge of the board, it's no surprise that you got nothing when measuring supply ground to the far left mosfet pin. They're directly connected. Measure to the pin farthest away from the power connectors for D10 (or all the way to the right). That pin is the gate pin and comes from the arduino. If you still have nothing, either your pins.h file is wrong and the Mega board isn't using the right pin, or your Mega board is toast somehow. If you measure ~5v but the LED still doesn't light, your MOSFET is fried. But that's easy to replace.
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BradStaff
Re: Hotend Problems
May 22, 2014 07:53PM
Well I just fried my Mega Board's voltage regulator. I'm replacing it with this.
[store.gravitech.us]
I think that there was a problem in the pins.h file but i wont know until I fix it.
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