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Issue with ramps 1.4

Posted by Usman1222 
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Usman1222
Issue with ramps 1.4
September 09, 2020 10:06PM
Hello i ordered a ramps 1.4 board and had an issue with bed heating so i measured the voltage from ground to (+) of D8,D9,D10 and it was 12volts which is boards input voltage. Then i messured the voltage from (+) to ground of D8,D9,D10 and i got 2-2.5 volts. Therefore i changed the mosfets and now i get 4.44 volts. When the load (heated bed, fan) is connected then the voltage across + and - terminals of D8,D9,D10 is the same which i measure from + to ground of D8 etc without load. Where is the issure in this ramps board?
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Dust
Re: Issue with ramps 1.4
September 09, 2020 11:06PM
On RAMPS the mosfets are used to switch the gnd pin.

the +pins on the mosfets are always the input voltage with respect to board gnd
the -pin on the mosfet when off is also the input voltage with respect to board gnd (the voltage comes through the heated bed)
the -pin on the mosfet when on is gnd with respect to board gnd so the difference from + to - mosfet pin should be 12v.


If your getting way less than 12v, your bed or your bed wiring may be bad or designed for 24v.

Edited 2 time(s). Last edit at 09/09/2020 11:10PM by Dust.
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Usman1222
Re: Issue with ramps 1.4
September 10, 2020 05:07AM
I am getting less than 12volts without connecting heated bed
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Dust
Re: Issue with ramps 1.4
September 10, 2020 06:42AM
Without the heated bed the pin is just floating. You need the bed to make any usable readings.
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Usman1222
Re: Issue with ramps 1.4
September 10, 2020 06:44AM
Even with the bed it gives same readings
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Dust
Re: Issue with ramps 1.4
September 10, 2020 07:22AM
Check the resistance of your bed and cables while unplugged. Should be very low, ie about 1.1 ohms.
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Usman1222
Re: Issue with ramps 1.4
September 10, 2020 07:34AM
0.03 ohm and it beeps when i test for continuity
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Dust
Re: Issue with ramps 1.4
September 10, 2020 07:56AM
a 0.03 ohm bed at 12v would be a 5 kilowatt heater!!! using 400 amps! (most are around 130 watts)

That is not right.

Edited 1 time(s). Last edit at 09/10/2020 07:57AM by Dust.
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Usman1222
Re: Issue with ramps 1.4
September 10, 2020 08:15AM
Its 0.3 ohm when i test for continuity but when i test it at 200 ohm then i get 1.3 ohm. One important thing that i have found out now is that on one of the boards that i have d8 led lights up when i have no wire connected to it. And when i connect heat bed onto D8 then the led never comes on.
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Roberts_Clif
Re: Issue with ramps 1.4
September 10, 2020 10:21AM
Is it possible that when the wires were soldered to the bed they were shorted.

If you could post a photo of the soldered connections we could look see if it is, if not shorted then it may be incorrectly wired or you may have a bad Hot bed.

Computer Programmer / Electronics Technician
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Usman1222
Re: Issue with ramps 1.4
September 10, 2020 10:48AM
I checked for continuity and my multimeter gave a beep. I set it to 200 ohm and it gave 1.3 ohm. Still is there a possibiloty that it may have shorted?
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Roberts_Clif
Re: Issue with ramps 1.4
September 10, 2020 11:30AM
Actually that is a good reading...

12 volts over 1.3 ohms = 9.23 amps = 110 watts

As another forum user stated
Quote
Dust
Check the resistance of your bed and cables while unplugged. Should be very low, ie about 1.1 ohms.

Computer Programmer / Electronics Technician
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Usman1222
Re: Issue with ramps 1.4
September 10, 2020 02:19PM
Are these connections correct?
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Ohmarinus
Re: Issue with ramps 1.4
September 10, 2020 02:30PM
Quote
Usman1222
Are these connections correct?
What type of bed is it? It's really impossible to say without any reference.

I also see two empty pads where I have LED's but I also know these are not needed.

http://www.marinusdebeer.nl/
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Usman1222
Re: Issue with ramps 1.4
September 10, 2020 02:33PM
Mk3 12/24V aluminium heated bed
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Roberts_Clif
Re: Issue with ramps 1.4
September 10, 2020 04:30PM
The image you posted appears to show it is wired for 12 volt use.

image attached


Computer Programmer / Electronics Technician
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Dust
Re: Issue with ramps 1.4
September 10, 2020 09:01PM
The soldering on the bed connectors is dreadful, needs the pads to have been much hotter.
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