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Tapping power from 1.0
#1
Please be brutally honest, Im not an electrical engineer. Is there any reason I shouldnt tap 5v and 12v for extruder fan from the power connections on the board/plug? Ive had a Pi plugged into 5v and havent really noticed any issues. For the 100th time I forgot to plug my extruder fan into the wall and I got pissed and wired it straight into the 12v plug. Aside from my current hazardous implementation, is there any reason to avoid stealing power from here?

Id like to avoid burning my house down or even worse, burning down my printer and my house. so hurl insults if necessary...please.

[Image: 2015-01-12%2021.57.05.jpg]
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#2
Ok, Ive printed an hour like this, tapping both 5v for the Pi and 12v for extruder fan. I sure would like to close this thing up and be done with all the wires hanging out of it. Im not looking to hold anyone liable, would just like to get some feedback on whether there is any inherent danger or concern about tapping power off the board plugs. Any input is welcome, seriously.
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#3
I'm very much interested in the very same thing, as my adventure to tap power from the LED bar didn't end up too well (board toasted). I was thinking of doing this too, but like you, I'm not 100% sure that it's the right thing to do.
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#4
Apparently its a taboo topic with 31 views and no replies, no one even bit to call me stupid! Im friends with several electrical engineers at work, the verbal abuse will be severe but I'll ask them today and post their feedback.
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#5
Spoke with a couple electrical engineers at work and they all agreed there is nothing inherently dangerous by tapping a 12v rail at the motherboard plug. They saw my pic and freaked out, which I expected, since there is a short concern with the way I have wires stuck into the plug with nothing securing them. Im being told there are two things to look out for, to make sure a 12v fan running between 1-2amps does not overload the power rating of the power supply or steal power from existing consumers. These guys jump at the chance to show me up since Im the expert in their current space, so I have one of them coming over this weekend to meter out whats being drawn with and without the fan. So Ill know for sure over the weekend but for now feel confident that Im not going to fry anything unless my McGyver wiring job comes loose, which it wont after short work with a soldering iron. Ill post pics of how I merged the additional leads with the existing, as well as communicating whats found after everything has been metered.

Im assuming no one replied because they dont want to be at fault for any screwup, so Im going to take the same stance here and add the disclaimer of doing this at your own risk. If you dont have the patience and wait for the professional analysis this weekend, I know I dont.....please be careful and make sure your connection is soild and periodically feel the wires to make sure they arent heating up and melting insulation.
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#6
haha I'll certainly wait for your data and pics Smile

In my case I need to tap power for the stock extruder fan though, and that one runs only at 5v and about 300mA (IIRC). I'd be interested in knowing how much current is going through the 5V socket.
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#7
So, You complain someone looked at your post without responding? What an interesting way of demanding an answer... PLEASE tell me you don't vote. Lol! Smile

No one knows the design specs of the power supply so no one can truly say what is safe or not safe. What I can tell you is i am running a pi, usb hub, camera, keyboard, mouse, wifi adapter, and an extra fan. I've been doing so for months. I based my doing this on standard engineering practice of a power supply being 20 percent or so larger than needed.

While pondering that thought, consider that an xyz *engineer* specifically told me using a 40 watt heater could shorten the life of the power supply because it was already running right near its limit. For me, i could care less because i have more than enough experience to repair the supply.

Point is, your experience might vary. Just because i do it doesn't mean you should. Go see my mcu replacement thread, as an example, because even most technicians simply can not change 144 pin mcu. If you truly want to be safe, use a separate power supply. Wink

But since you wanted someone to call you stupid, I'm going to say your method of testing for overloads by the melting of wires is absolutely state-of-the-art intriguing! Best laugh i had all day! Smile Smile


As for sourcing power from the leds, this is not a good idea and could easily damage the controller board. If you must tap power, you should do it at the power supply connector and you SHOULD insert a suitable fuse to help protect against fire/damage of an overload does occur. (Much the same way the oem board is fused right after power enters the board from that connector. )

Don't let the smoke out, that's the secret ingredient that lubricates the electrons.
.

Kieth
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#8
If I came off as complaining, Im sorry you took it that way. I thought I effectively conveyed why I thought (with good reason) folks were not replying. All of my posts are light hearted and jovial, i thought that came across without peppering every sentence with a smiley face. I dont know how im coming off as demanding as Im careful to not come off as a entitled and expect folks to jump to my assistance...which seems to be the world view of folks in the US. Wink Wink Im excited as hell about 3d printing and possibly I get a little too chatty about it.

Anyway, I was able to bribe our building electrical engineer over last night with the promise of custom legos for his daughter. He ran his multimeter in series with both the heatbed and the extruder heater. He indicated that the 12v , .08amp fan I need to run for the e3d posed no risk , and in fact I should be able to run a couple of them without coming close to overloading the power supply, from the data he collected. He cut 2 of my 12 volt leads, crimped my fan wires onto it, and inserted back into the molex connector. Same way I had it wired minus the crimp. I asked about shorts or possibly frying the board and he said since it was not inbound power and the draw was low, there was no concern and doing this is very common in field HVAC repair. As with everything though, grain of salt, which is why I was asking for multiple opinions.

I havent melted any wires, and was advising folks to be mindful of it. With electricity its a fine line between trying to help someone and them burning their house down, since you arent aware of everyones skillset in that area. But I am glad I gave you the best laugh for the day! Smile Smile Smile

This is my favorite forum for the davinci (not many to chose from, i know) , and I dont want to risk being booted by coming off as an asshat. Kieth, I appreciate all your posts and will read the mcu thread you referenced.
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#9
Nah, i took it as sarcasm. Hence the Smile Smile

Kieth
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#10
Quote:I'm very much interested in the very same thing, as my adventure to tap power from the LED bar didn't end up too well (board toasted). I was thinking of doing this too, but like you, I'm not 100% sure that it's the right thing to do.

Oscahie, Let me know if you want me to provide more detail on this topic. My friend said that as long as Im not adding over 1000ma to the 12v rail I should be fine. I didnt have him probe 5v because Ive been running my Pi with wireless adapter and raspicam for at least a couple months now with no adverse impact that Ive seen.

Even though this can be done, I plan to have a PC power supply next to the printer and plug everything in there . Ive integrated a couple bright LED's into my object fan, since it shades the overhead LED, but Im not going to push it and plug that into the davinci power supply. I also plan to add an additional camera and exhaust fan and I might as well move all the additions to a separate supply. Just because you can do something doesn't mean you should, and Ive gotten off lucky so far with my late night frustration hacks.

Just out of curiosity, did you fry the board the LEDs are on, or the mainboard fried?
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#11
I fried the mainboard... but it was entirely my fault, I possibly shortcut the wires that power the LED bar while I was manipulating them. I had it working for a while and it was working well (stock extruder fan running at 8.8v), the only downside being that the LEDs would not turn off anymore when the fan was sucking power from them.

So you have plugged a Raspberry Pi to the 5v line or just to the USB port? If the former, how exactly did you do it, soldered?
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#12
Ive got the printer USB running back into the unit, running to the Pi (pi sits on the shelf that holds the top Zaxis rods in) , and then the Pi wired into the power supply plug at the mainboard. On my pic above its the black wire sitting on top of the plug. Ive since re-crimped the power supply plug to include my stuff, versus just having a tinned wire poking into the back of the plug. I can post a small pic to illustrate if you want. A cheap $15 PC power supply might be the easier route unless you are used to doing this type of thing, and the only "hack" youd have to do there is short the ATX pins that turn the power on.
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#13
Kieth, I'm running a 40W heater cartridge now (after double checking it was working well, as you mentioned in another post) and an extra 5v fan. What do you think would be the worst case scenario, just buying a new power supply or could also the control board get damaged?
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#14
Obviously their is never any guarantee, but assuming they followed standard design practice of 20% safety margin, it is my *opinion* you likely wont see an issue. With the heater change and fan additions you should be talking about a half amp difference in current levels. For something as power hungry as a printer a 6 watt difference is within the 20 percent. ( the extruders 35 watt heater alone - if in fact there is a 20% tolerance- would be enough to make up for the fan and 40 watt heater, and thats before we consider the bed heater, steppers, etc)

Like I say, Ive been running the usb hub (12v), fan (12v), pi (5v), usb cam, wifi dongle, wireless keyboard/mouse, etc for months without issue. My MCU glitching failure was caused by a defective heater burning a component on the motherboard. (search mcu black bars) and was nothing to do with tapping power...

Kieth
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#15
This fan you're talking about, it's the 40mm stock extruder fan right? The load on that is likely less than 50mA, you should be fine tapping power from pretty much anywhere to run it. I've personally tapped the +5V supply to run mine. There's no on/off for it of course except for the primary power switch, but at least I never need to worry about not having it on.
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