20Volts on the 11amps input ?
Posted by Replace
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20Volts on the 11amps input ? January 07, 2015 04:56AM |
Registered: 13 years ago Posts: 861 |
My Orca ran on Gen6 with 12V for the motors and 20V for the heated bed.
Now, after the Gen6 failed, I have rebuilt my Orca on Arduino Ramps.
Currently I have 12V on both inputs, but my Heated bed is 'slow'.
Can I just put the 20V power source into the 11A input terminal ?
Or will that fry the Ramps board ?
Thomas
Edited 1 time(s). Last edit at 01/07/2015 04:57AM by Replace.
www.3daybreaker.blogspot.com
Orca V4.4 rebuild to Ramps with Mk8 and E3D, as well as a Rostock Delta Mini and an OLO in backorder :-)
Now, after the Gen6 failed, I have rebuilt my Orca on Arduino Ramps.
Currently I have 12V on both inputs, but my Heated bed is 'slow'.
Can I just put the 20V power source into the 11A input terminal ?
Or will that fry the Ramps board ?
Thomas
Edited 1 time(s). Last edit at 01/07/2015 04:57AM by Replace.
www.3daybreaker.blogspot.com
Orca V4.4 rebuild to Ramps with Mk8 and E3D, as well as a Rostock Delta Mini and an OLO in backorder :-)
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Re: 20Volts on the 11amps input ? January 07, 2015 05:22AM |
Registered: 10 years ago Posts: 14,672 |
Looking at the schematic at [reprap.org], the +12V input on pin 1 of the power connector only feeds the 11A fuse and hence the heated bed circuit. The mosfet is rated at 60V. So putting 20V on that input should be fine. The heated bed LED will be a little brighter and the resistor next to it will get a little warm, but nothing to worry about. Check that your heated bed will not draw more than about 10A when you feed it from 20V.
Don't put 20V into the other 12V input, because the capacitors on many RAMPS boards are rated at 16V.
Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod
Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].
Don't put 20V into the other 12V input, because the capacitors on many RAMPS boards are rated at 16V.
Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod
Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].
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Re: 20Volts on the 11amps input ? January 07, 2015 05:51AM |
Registered: 13 years ago Posts: 861 |
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Re: 20Volts on the 11amps input ? January 07, 2015 07:12AM |
Registered: 13 years ago Posts: 861 |
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Re: 20Volts on the 11amps input ? January 07, 2015 08:20AM |
Registered: 10 years ago Posts: 869 |
A standard RAMPS board will have two polyfuses near the main power connection. They are usually square yellow components that stand off the board vertical. They are self resetting and operate by increasing resistance as they heat up do to current draw until they reach a point where it's essentially an open circuit. Once they cool to a point they will reset and conduct again. They can be replaced with a different style of fuse if you prefer.Quote
Replace
I did not even know a fuse was included.
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Re: 20Volts on the 11amps input ? January 07, 2015 10:42AM |
Registered: 14 years ago Posts: 1,092 |
Just of note:
The 11A polyfuse is only rated for 16V. This means that if your bed develops a short, you'll be putting too much voltage into the polyfuse.
Too high a voltage with a short can result in the polyfuse actually catching fire (yeah - this is why I hate polyfuses).
It's recommended to replace the 11A polyfuse with a real 15A fuse (eg: an automotive blade-style or even just a standard 3AG fuse in an external fuse holder soldered to the board) if you're using it with >15V.
The 11A polyfuse is only rated for 16V. This means that if your bed develops a short, you'll be putting too much voltage into the polyfuse.
Too high a voltage with a short can result in the polyfuse actually catching fire (yeah - this is why I hate polyfuses).
It's recommended to replace the 11A polyfuse with a real 15A fuse (eg: an automotive blade-style or even just a standard 3AG fuse in an external fuse holder soldered to the board) if you're using it with >15V.
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Re: 20Volts on the 11amps input ? January 07, 2015 10:56AM |
Registered: 10 years ago Posts: 14,672 |
Quote
Cefiar
Just of note:
The 11A polyfuse is only rated for 16V. This means that if your bed develops a short, you'll be putting too much voltage into the polyfuse.
Too high a voltage with a short can result in the polyfuse actually catching fire (yeah - this is why I hate polyfuses).
It's recommended to replace the 11A polyfuse with a real 15A fuse (eg: an automotive blade-style or even just a standard 3AG fuse in an external fuse holder soldered to the board) if you're using it with >15V.
Good point, I had forgotten that.
Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod
Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].
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Re: 20Volts on the 11amps input ? January 07, 2015 12:09PM |
Registered: 13 years ago Posts: 861 |
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Re: 20Volts on the 11amps input ? January 07, 2015 04:40PM |
Registered: 10 years ago Posts: 14,672 |
Only if you short-circuit the heat bed output.
Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod
Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].
Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod
Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].
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Re: 20Volts on the 11amps input ? January 07, 2015 05:27PM |
Registered: 13 years ago Posts: 861 |
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Re: 20Volts on the 11amps input ? January 07, 2015 05:30PM |
Registered: 9 years ago Posts: 1,159 |
Quote
Replace
So, why is a 16V polyfuse more dangerous than a 12V car fuse on a 20V power line ?
Because the car fuse can not get on fire ?
Because a car type fuse is not voltage sensitive it will blow at a certain current whereas a polyfuse when fed with to much voltage at it's trip points can burst into flames.
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Re: 20Volts on the 11amps input ? January 08, 2015 10:02AM |
Registered: 13 years ago Posts: 861 |
Ok,
I will see whether I can replace these fuses with a car fuse socket.
Thanks for the warnings. Better safe than sorry.
Are there solder-on sockets for the 12V car fuses ? I mean the blade ones, not the glass tubes.
Edited 1 time(s). Last edit at 01/08/2015 10:02AM by Replace.
www.3daybreaker.blogspot.com
Orca V4.4 rebuild to Ramps with Mk8 and E3D, as well as a Rostock Delta Mini and an OLO in backorder :-)
I will see whether I can replace these fuses with a car fuse socket.
Thanks for the warnings. Better safe than sorry.
Are there solder-on sockets for the 12V car fuses ? I mean the blade ones, not the glass tubes.
Edited 1 time(s). Last edit at 01/08/2015 10:02AM by Replace.
www.3daybreaker.blogspot.com
Orca V4.4 rebuild to Ramps with Mk8 and E3D, as well as a Rostock Delta Mini and an OLO in backorder :-)
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Re: 20Volts on the 11amps input ? January 08, 2015 10:09AM |
Registered: 10 years ago Posts: 869 |
For fuses, the primary concern is preventing arcing even after the fuse has been blown. Or in the case of a polyfuse, arcing through the polymer. The rated voltage is the maximum voltage the fuse is designed to protect against. Fuses can almost always be operated at voltages lower than what their rating is, current is the rating that is most important as that is what the fuse is protecting. Automotive style blade fuses have a minimum voltage rating usually of 32V DC so running it at 20V isn't a problem.Quote
dougal1957
Because a car type fuse is not voltage sensitive it will blow at a certain current whereas a polyfuse when fed with to much voltage at it's trip points can burst into flames.
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Re: 20Volts on the 11amps input ? January 08, 2015 12:02PM |
Registered: 13 years ago Posts: 861 |
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Re: 20Volts on the 11amps input ? January 08, 2015 12:49PM |
Registered: 9 years ago Posts: 1,159 |
Quote
Replace
Yes I get that.
Now I would like to get a link to a socket for those fuses that I can older in place of the Poly
here you go
Mini Automotive Blade fuse holder
Sure you can find something like this as I don't know where you are in the world?
Doug
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