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Voltage max for Ramps 1.4

Posted by Bmeehan19 
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Bmeehan19
Voltage max for Ramps 1.4
October 06, 2016 09:43AM
Hi,
Ive read through a ton of posts/threads about voltage input to Ramps 1.4. I have an adjustable output 12v 25A PSU and want to use a MK3 heated bed but read stories of slow to insufficient heating of the bed at 12v but adequate heating at 13.8v I found a bunch of people saying Ramps can support up to 13.8v without any damage to any components on the board. Then I also found some (not as many) saying that 12v is the max or you will damage some components. Now I know I will need cooling and possibly a heatsink. I will have 2 dedicated fans on all the time blowing on the Ramwps board so cooling should be sufficient. Can we put this voltage discrepancy thing to bed?

Thanks for your input

Bryan
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stephenrc
Re: Voltage max for Ramps 1.4
October 06, 2016 10:35AM
What determines the max voltage a RAMPS can take are the PTC fuses and the capacitors.
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Bmeehan19
Re: Voltage max for Ramps 1.4
October 06, 2016 10:51AM
Would you be willing to tell me where to check on my board so I can check which ptc fuses and capacitirs I have are? Then I can determine my max voltage.
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dc42
Re: Voltage max for Ramps 1.4
October 06, 2016 11:38AM
Those capacitors are always rated at 16V or occasionally more. I think the 11A fuse is also rated at 16V.

The component you are most likely to damage by increasing the voltage to about 14V is the 5V regulator on the Arduino. If you have an LCD attached then it may be running very hot already, unless you are supplying the 5V power through the USB port. You could connect 2 or 3 1N4001 or similar silicon diodes in series with D1 to take up the extra voltage, or remove D1 and provide external power. Or replace the Arduino by a Taurino.


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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Bmeehan19
Re: Voltage max for Ramps 1.4
October 07, 2016 08:30AM
Are there any other components like fans etc that may not like more than 12v? I am going to have to 5v blowers for print fans running off a strp down converter. Should I do the same for anything else? Meaning using a step down from 13.xx to 12v?
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dc42
Re: Voltage max for Ramps 1.4
October 07, 2016 10:43AM
Most 12V fans are rated to 13.2V and in practice 14V doesn't harm them. If it worries you, connect 1 or 2 1N4001 or similar diodes in series with the fan.

Edited 2 time(s). Last edit at 10/07/2016 12:44PM by dc42.


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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gbr1918
Re: Voltage max for Ramps 1.4
October 07, 2016 11:47AM
I'm using a 12V psu (cheapo, came with my made-in-china prusa i3) to power the extruder heat and the RAMPS 5V via the voltage regulator. The heated bed is fed by a 24V 40W psu made by XP Power. This is just getting switched by the mosfet on the RAMPS board, so using 24V is no prob and gets the bed up to ABS temperature (110 degrees C) in minutes rather than hours. Also, I have the bed mounted on millboard and drop an insulating pad on while I'm warming up, which both speed things up a bit. Initially I was using the 12V supply to run the whole thing, and it couldn't do it: the bed temperature would drift down 20 degrees while printing and the printed object tended to ping off the bed sad smiley !
I'm not using a fan on the RAMPS board: nothing on there hot enough to require it.

Dave

Edited 1 time(s). Last edit at 10/07/2016 11:49AM by gbr1918.
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Bmeehan19
Re: Voltage max for Ramps 1.4
October 09, 2016 08:11PM
I decided to use a 12v 200w silicone heater for the bed. If I pit 13.5v to it I think that calculates out to 15amps. I must change my ptc fuse to a 15a auto style, add two more diodes to the already existing D1 diode so I dont burn out the arduino right? Also do I need a different mosfet for the heated bed? I will have two fans on 100% speed blowing on the ramps at all times.

Thanks
Bryan
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dc42
Re: Voltage max for Ramps 1.4
October 10, 2016 03:34AM
You will probably burn out the traces or the connectors on the RAMPS if you run the heated bed at much over 10A even if you do use a more suitable mosfet.

A 12V 200W bed heater will draw 16.7A at 12V. If you want to use a bed heater with more than about 150W power then I suggest you use 24V power.


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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Bmeehan19
Re: Voltage max for Ramps 1.4
October 10, 2016 08:18AM
Yet another blunder on my part. I already ordered the 12v silicone heated bed. Can I use a SSR to power it from my current 25A power supply and just use D9 as the trigger? Would that provide enough power? What if I bump up my output voltage to 13.xx? Would that help it heat faster?
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dc42
Re: Voltage max for Ramps 1.4
October 10, 2016 08:29AM
Yes you can use a DC-DC SSR but you need to choose it carefully. See [duet3d.com] for SSR recommendations. Although that is a support page for the Duet and Duet WiFi, the SSR recommendations are good for other electronics too. [btw we have already qualified the Duet WiFi for 15A bed heater current and we are hoping to increase this to 18A.]

If you stay with your existing bed heater, increasing the supply voltage to 13.2V will give you 21% more heating power. Using 14V will give you 36% more heating power. Replacing the bed heater mosfet on your RAMPS and the large polyfuse by an auto fuse will also give you a few percent increase.

Edited 2 time(s). Last edit at 10/10/2016 08:31AM by dc42.


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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Bmeehan19
Re: Voltage max for Ramps 1.4
October 10, 2016 11:29AM
Well I just ordered the Auber SSR suggested in the link so do I still need to change my polyfuse and mosfet?
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dc42
Re: Voltage max for Ramps 1.4
October 10, 2016 12:37PM
Quote
Bmeehan19
Well I just ordered the Auber SSR suggested in the link so do I still need to change my polyfuse and mosfet?

No need to change them.


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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Bmeehan19
Re: Voltage max for Ramps 1.4
October 10, 2016 03:59PM
I added 3 more diodes to D1 which makes 4 in total. Each one dropped the voltage around .32v so having my psu at 13.8v Im getting appx 12.5v after the diode. The Arduino can handle that voltage with a full graphics LCD correct?
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dc42
Re: Voltage max for Ramps 1.4
October 10, 2016 04:30PM
I think you will find that with the Arduino connected, the voltage drop is more like 0.7V per diode.


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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Bmeehan19
Re: Voltage max for Ramps 1.4
October 10, 2016 05:41PM
Ahhh! Do I measure this in the same place, right where the diode meets the board or sonewhere else?
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Bmeehan19
Re: Voltage max for Ramps 1.4
October 10, 2016 08:45PM
Well. Something happened. After I added the diodes to D1 the arduino wont power on and I have no power to my stepper drivers. I did all the soldering with nothing plugged into ramps and ramps not mounted to arduino. I have power on both sides of the 5a ptc. I have power on both sides of D1 i have power on the "silver line" side of D2 no power on the "black side" of D2 and no power going into arduino. I did replace D2 as I had an extra one and same result. What did I mess up?
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dc42
Re: Voltage max for Ramps 1.4
October 11, 2016 04:10AM
Please show us your wiring. I suspect you have D2 connected the wrong way round. +12V-ish power should go in on the black side and come out (around 0.8V lower under load) on the silver line side.


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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Bmeehan19
Re: Voltage max for Ramps 1.4
October 11, 2016 08:45AM
With the power terminal oriented at the bottom left corner while looking down at the ramps the silver line is on the top. It all worked with the ramps test file through arduino while hooked to the psu before I added more diodes to D1. I bet I shorted something. With my ohm meter I get resistance between the + / - on the 5a sode and no resistance on the 11a side. Not sure if that indicates a problem in the 5a circuit or because there are diodes , capacitors etc on that circuit. I didnt test it prior to doing any work on it so I have no comparison.
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Bmeehan19
Re: Voltage max for Ramps 1.4
October 15, 2016 11:01PM
Well I bought a new ramps board. It still does not power up the Arduino. Both D1 and D2 diodes check out at .5v which from what I read that means they are good. Could it be my voltage regulator on my arduino? When powered through USB it powers right up. I check voltage on the gnd and 5v pins on the arduino and had 4.92v so power is getting through there. Could that be my problem?

Here is a pic of my ramps.
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dc42
Re: Voltage max for Ramps 1.4
October 16, 2016 05:36PM
Yes it could be the 5V regulator on the Arduino. Do you have around 12V between the Arduino VIN pin and ground?


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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Bmeehan19
Re: Voltage max for Ramps 1.4
October 17, 2016 08:48PM
I didnt check the voltage at those pins. However I just replaced the regulator and now I get power to the Arduino! My lcd lights up and I can control my steppers.

Thank you all for the help!! What a feeling of accomplishment!
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