RAMPS and D1 diode February 10, 2015 02:49PM |
Registered: 9 years ago Posts: 44 |
Re: RAMPS and D1 diode February 10, 2015 04:02PM |
Registered: 10 years ago Posts: 869 |
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kreidler
1. I want to use the PS-ON on the RAMPS for switching the ATX-PSU. I assume that I have to connect additionally the 5V standby from the PSU to the 5V rail located near to the PS-ON. Correct?
Nope. doesn't matter. D1 just connects the 12V input of the RAMPS to the voltage regulator of the Arduino. The only time that you need to remove it is if you're running voltages higher than 12V on the RAMPS input. The Arduino can't handle higher voltage, it'll over heat and cook the regulator.Quote
2. For the beginning I would like to have USB permanently connected to the Arduino. Later on a raspberry may do the job on the same line. Do I have to remove D1 in this case or does it not matter if the RAMPS supply voltage will be around 12V?
If you remove the diode, you have to power the arduino with either the barrel connector or via USB.Quote
2a. If the diode has to be removed, can I use as a workaround an USB data cable without the 5V connection?
Re: RAMPS and D1 diode February 11, 2015 08:02AM |
Registered: 9 years ago Posts: 100 |
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Without D1 installed, or when the 12VIN is not connected, the Arduino gets its power from USB. If you want your kit powered without USB connected you need to solder in D1 OR connect VCC to your PSU.
The VCC pin can be connected to your ATX's 5Vsb to continuously power the Arduino from your ATX power supply. You will want to make sure that D1 is not installed or cut out. The Arduino is not designed to be powered directly on the VCC rail and the VIN pin at the same time.
If you want to use PS_ON to turn on your power supply then don't use diode D1, you need your Arduino to be powered from 5Vsb otherwise when no USB is connected the PS_ON pin floats (and your power supply pulses on and off).
Re: RAMPS and D1 diode February 11, 2015 08:37AM |
Registered: 10 years ago Posts: 14,672 |
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cdru
The only time that you need to remove it is if you're running voltages higher than 12V on the RAMPS input. The Arduino can't handle higher voltage, it'll over heat and cook the regulator.
Re: RAMPS and D1 diode February 11, 2015 11:29AM |
Registered: 10 years ago Posts: 869 |
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dc42
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cdru
The only time that you need to remove it is if you're running voltages higher than 12V on the RAMPS input. The Arduino can't handle higher voltage, it'll over heat and cook the regulator.
This is a common piece of misinformation. The Arduino is rated for up to 20V input. If you have nothing running from the 5V rail apart from the RAMPS, you can quite safely run the Arduino with 15V input, possibly a little more (but many RAMPS boards have capacitors rated at only 16V).
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The board can operate on an external supply of 6 to 20 volts. If supplied with less than 7V, however, the 5V pin may supply less than five volts and the board may be unstable. If using more than 12V, the voltage regulator may overheat and damage the board. The recommended range is 7 to 12 volts.
Re: RAMPS and D1 diode February 11, 2015 12:26PM |
Registered: 10 years ago Posts: 869 |
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plankton
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If you want to use PS_ON to turn on your power supply then don't use diode D1, you need your Arduino to be powered from 5Vsb otherwise when no USB is connected the PS_ON pin floats (and your power supply pulses on and off).
The 3 pins next to the reset button on RAMPS are VCC, PS_ON, and 5V
So disconnect D1, and attach your PSU 5VSB to VCC (this will power your Arduino), attach PS_ON to your power supply PWR_ON, and leave 5V unconnected (unless you need to power servos, in which case you would connect it to the PSU 5V rail (not the 5VSB )).
Re: RAMPS and D1 diode February 11, 2015 01:32PM |
Registered: 10 years ago Posts: 14,672 |
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cdru
Perhaps I should temper my wording to say that may overheat instead of it will. But when Arduino themselves say that it's not recommended to run it over 12V, then I'm going to tend to believe the people that created it.
Re: RAMPS and D1 diode February 11, 2015 01:58PM |
Registered: 9 years ago Posts: 100 |
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cdru
How confident are you that your 5VSB is exactly 5V and you won't draw more current than the Arduino traces can handle?
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cdru
The Vcc pin you are talking to can supply the Arduino, but it bypasses the regulator and is not advised to use. The 3 recommended ways of powering an Arduino are the USB connection (polyfuse protection of 500ma), barrel connector (1A polarity protection diode), and Vin pin (no current protection I believe). The Vin pin is what is connected to D1 on the RAMPS board
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cdru
Attach the 5VSB and ground wire to a barrel connector and plug that into the Arduino.
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Arduino
The board can operate on an external supply of 6 to 20 volts. If supplied with less than 7V, however, the 5V pin may supply less than five volts and the board may be unstable
Re: RAMPS and D1 diode February 11, 2015 03:13PM |
Registered: 10 years ago Posts: 869 |
Judging from the average post here or in an Arduino form, I'd say that the former is more likely. They didn't say that you couldn't use it with higher voltages, just that it's not recommended.Quote
dc42
The Arduino.cc guys evidently either think most Arduino users are too stupid to be able to work out the power dissipation in the regulator for themselves, or can't be bothered to explain how to do it.
That's like stating how much gas a car uses when it idles. Who cares, because it's not doing anything. You have to load the car and move at a particular speed in order to do something useful. Likewise, an unloaded Arduino just sits there. If it's not calculating something, or controlling pins to do things, it's of no use. And since an Arduino is designed to do whatever the user wants and not some single fixed task, they can't say how much current is the limit. Is it making an LED blink? Or running a LCD display? Or utilizing an Ethernet shield? All 3 things are going to have very different current utilization.Quote
Neither can they be bothered to specify how much current an unloaded Arduino takes, which is necessary to know in order to work out the power dissipation.
The spec sheet for the regulator says the maximum power dissipation can be computed, for an ambient air temp of 20C and a thermal pad of 7.5mm square by (150C - 20C) / 120 C/W = 1.08 Watts. So your 90mW + 55mW load running at 15V = 1.45 watts to dissipate, exceeding the maximum unless a heat sink or air flow can help the dissipation. At 12V, the 145mW load has 1.02 watts dissipated, right at the upper limit without additional cooling. If I'm misunderstanding the details behind this, educate me where I'm doing something incorrectly.Quote
I measured the current consumption of an Arduino + RAMPS at 90mA. At 15V input, this gives a power dissipation in the regulator of about 0.8W, which the regulator should be able to handle without difficulty. Given the way the regulator is mounted, I would be comfortable dissipating about 1W in it. I can keep my finger on the top of the regulator, which confirms that it is not overheating. But if you add a 12864 LCD with a current draw of 55mA to an Arduino/RAMPS, then even at 12V input that's 0.9W dissipated in the regulator - more than an unloaded Arduino/RAMPS with 15V input.
Re: RAMPS and D1 diode February 11, 2015 03:26PM |
Registered: 10 years ago Posts: 869 |
I would agree on voltage is more a concern than the current, but current shouldn't just be forgotten about. People try to run a servo. Or a motor. Or a fan. Or there's a short. Or... there's many ways that someone might exceed what otherwise would be protected even if it's minimal protection.Quote
plankton
I think the concern is that powering via the 5V pin bypasses the voltage regulator, providing more than 5V could damage the Arduino. Current draw is a function of voltage and resistance, a badly regulated PSU isn't going to "push" more current through the board unless the Arduino has a short (which lowers the resistance).
I power my arduino and rpi with a 5VSB through the barrel connector, as well as have D1 in place so it could get power through the normal 12V input. When my Pi needs to turn on the printer, it sends M80 which grounds the PS_ON pin turning on the ATX power supply giving full power to the Arduino, heated bed, fans, etc. When it's done printing, M81 brings PS_ON high turning off the power supply. The Arduino then resumes running off of 5VSB. The arduino doesn't care if it receives different voltages and both circuits are protected from back feeding one another either by the polarity protection diode for the barrel connection or D1 on the RAMPS board. And since you'd be using a common ground for everything, that's not a problem either.Quote
Agreed that's what Arduino recommend, but if you want to turn off your power supply with G-code then you need to power the Arduino from 5VSB (unless you use a separate external 12v supply, which rather defeats the purpose), so that's your only choice.
The arduino will basically be idling with no real load, so it still works. Once you need it to work under a load, the power supply will have been turned on and 12V will be present.Quote
cdru
So using 5VSB to power the board via the barrel connector is not a good idea.
Re: RAMPS and D1 diode February 11, 2015 05:25PM |
Registered: 9 years ago Posts: 44 |
Re: RAMPS and D1 diode February 12, 2015 03:57AM |
Registered: 9 years ago Posts: 44 |
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cdru
I power my arduino and rpi with a 5VSB through the barrel connector, as well as have D1 in place so it could get power through the normal 12V input.
Re: RAMPS and D1 diode February 12, 2015 09:56AM |
Registered: 10 years ago Posts: 869 |
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kreidler
1. If D1 on RAMPS is installed, 12V supply is connected to RAMPS, these 12V are going directly to the Arduino via Vin into the regulator NCP1117 having fixed output of +5V on at least 6.5V input. Delivering at least 1A.
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2. If the Arduino is (additionally) connected through the barrel connector with 5V(SB ) this will end in a regulated voltage less than 5V according NCP datasheet. Nevertheless switching with G codes seems to work.
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3. +5V on the Arduino will be supplied either by Vin via! regulator (if D1 installed) or by USBVcc 'via' MosFET T1. Mega2560 scheme
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4. If Vcc pin on RAMPS is not connected this pin gets +5V from the Arduino.
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So, 'correct' way would be to remove D1 from RAMPS and connecting 5VSB to Vcc on RAMPS. In any case I will give the barrel connector a try.
Re: RAMPS and D1 diode February 12, 2015 10:39AM |
Registered: 10 years ago Posts: 869 |
I use an old micro-usb cable that I clipped one end off and just connected the outside two power wires to 5VSB and ground from the ATX power supply. To those same connections I connected the ardiono's barrel connector I clipped from an old wall transformer power supply that was the right size.Quote
kreidler
Just for my understanding: You are powering the Pi through the Arduino barrel connector only or do you have Micro-USB on the Pi connected to PSU+5VSB also?
Re: RAMPS and D1 diode February 12, 2015 01:52PM |
Registered: 9 years ago Posts: 44 |
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cdru
I use an old micro-usb cable that I clipped one end off and just connected the outside two power wires to 5VSB and ground from the ATX power supply. To those same connections I connected the ardiono's barrel connector I clipped from an old wall transformer power supply that was the right size.Quote
kreidler
Just for my understanding: You are powering the Pi through the Arduino barrel connector only or do you have Micro-USB on the Pi connected to PSU+5VSB also?
Re: RAMPS and D1 diode February 12, 2015 03:16PM |
Registered: 10 years ago Posts: 869 |
Early RPis were not able to output enough power via the USB ports. The RPi's USB ports had 140mA polyfuses and at 100ma, the resistance increased to a point where the voltage dropped to about 4.5V. Add in a USB wifi dongle and you can run out of power on those RPi. You can get around this by using a power USB hub, but the wiring just gets a little complicated and not worth the hassle. You'd still have to power the powered hub so you still have as many power connections, you're just moving where they connect.Quote
kreidler
Please correct me if I am wrong.
You have a micro-USB cable from 5VSB to RPi and a barrel connector from 5VSB to Arduino. Additionally you have an USB cable between RPi and Arduino.
If the PSU is off (no 12V on Vin) you should be able to remove the barrel connector from the Arduino without any change in system behaviour because the Arduino will be powered with stable 5V from the USB on the RPi and not via the barrel connector.
Re: RAMPS and D1 diode February 12, 2015 03:50PM |
Registered: 9 years ago Posts: 44 |
Re: RAMPS and D1 diode February 12, 2015 05:01PM |
Registered: 10 years ago Posts: 869 |
Re: RAMPS and D1 diode May 06, 2015 10:55AM |
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Re: RAMPS and D1 diode May 07, 2015 06:03PM |
Registered: 9 years ago Posts: 2 |