Another thanks to edirol, it took me a while, but your scheme works a treat!
I installed a 1.3 ohm Mk2 heatbed and powered everything from a 12V ATX PSU. I used the 8 pin EATX connector which is rarely used anyway, with half the wires going to the controller, and the other half to the heatbed over Edirols scheme, so I do not to risk overloading the controller and its connectors by pulling 15A or so from it. Heatbed heats up to 50C in a blink of an eye, and 100C in mere minutes.
Feature request!
It would be handy to have a switch to quickly start preheating the bed or turn it off. How hard would it be to add a two or three way switch to this scheme so that you can have:
?
[quote=“P4man”]
It would be handy to have a switch to quickly start preheating the bed or turn it off.
?[/quote]
P4man
Overriding the heat bed seems to me a danger issue, so I dont (want) to provide a solution here:
Cheers
I dont know about your heatbed, but mine cant exceed ~120C no matter what, so “always on” really is no different from setting 120C+ in software. And sure, you can do it in software, but my printer is not in the same room as my workstation (Im using octopi), sometimes its just convenient, like when you are preparing the print surface, when you are done you can start heating it without having to go to another room/pc first. Saves me a few minutes and a few stairs :).
Anyway, it was just a thought.
P4man, if you still insist, a 3-way switch S1 (on/off/on) could be added as follows:
Use at your own risk!
Hi P4man,
maybe I’m wrong, but it seems to me you won’t save so much, since you would have to go back and put your override switch back in the “auto” position after starting the print, so you’d have temperature control in the ATmega. Or how did you want to use this?
@edirol: basically, a push button and a non(!)-retrigerable monoflop could be used to implement a time-limited heating function, which would at least be a little more on the safe side.
Anyways, an LCD display (which works in parallel to Octopi) would probably be the best solution, since they usually have specific ABS and PLA preheat functions integrated, which use the temperature control of the board and have a time limit, too.
Cheers,
kuraasu
Hi edirol,
NB: R3 should be rated at least 1/4 W in this version.
Cheers,
kuraasu
[quote=“edirol”]P4man, if you still insist, a 3-way switch S1 (on/off/on) could be added as follows:
Use at your own risk![/quote]
Thanks, I appreciate it. I figured it couldnt be hard, but Id rather not guess where to put it :).
Sure, but I can flip that switch at any point, even when the print is already in progress. That doesnt cost time, not being able to heat to bed until I connect to octoprint, does cost time :).
[quote]Anyways, an LCD display (which works in parallel to Octopi) would probably be the best solution, since they usually have specific ABS and PLA preheat functions integrated, which use the temperature control of the board and have a time limit, too.
[/quote][/quote]
Yeah, ill end up with one of those eventually Im sure. I suppose it could also be done by using some GPIO pins on the raspberry if someone would write the code. You could also implement pauze and abort buttons, homing, etc. Pretty much eliminating the need for the lcd. Except for the LCD part :p.
Indeed, in this case, where the printer is in a different room and even a stairway between, a LCD addon is a “must have” IMHO.
Thank you for clarify
Well I have a laptop, a smartphone and a tablet I (can) use to control the printer locally, but the laptop isnt always at the printer obviously, and my smartphone and tablet struggle a bit with the octopi webinterface. So yeah, Ill probably get an LCD at some point, even though it seems a bit silly when you already have a networked Pi and all that mobile computing stuff.
Hi,
I have also upgraded to an additional 24V power supply for the heatbed.
I used a automotive relais to switch it on and of.
The relais can handle max 20A at 28VDC, a lot more than i wil use.
I placed a diode over the coil to protect the electronics.
I think this relais wil work a long time before failure so what are the (other) advantages to use an electronic switch in stead of a relais.
Hello all
I was following this thread for quite some time as I too want to boost the heating time of bed and extruder. 15+ minutes for the bed to get to 55 degrees (with mirror) is outside convenience.
As I dont like to have too many side packs around the printer, I was investigating a little more into the idea to drive the whole thing with one 24V power supply. I came up with the following plan:
The additional 5V USB outlet can be used for the OctoPi alimentation(!)
AFIK this should work, I am just unsure about the Voltage settings on the stepper motor drivers as I will have 24V instead 15V as driving motor voltage. Does anyone have an idea here? Or am I missing something crutial elsewhere?
Any feedback welcome.
Cheers
Mac
Hi SwissMac,
two (unfortunately negative) feedbacks from my side:
That’s too small. Count the heatbed in for 100 W when running on 24 V. When it’s hot, the resistance is increased and power consumption goes down to around 80 - 90 W, but when cold it can easily draw more than 4 A. The stock hotend cartridge would use more than 75 W if I remember correctly (and if it survives, it’s most likely a 12 V type). A replacement cartridge should have 30 W like before, or 40 W, which may be more easily available. Plus peak (!) power comsumption of the motors (range 1 to 2 A, for high accelerations even more), I’d say you’re looking at 200 W absolute minimum. And that’s with nearly no reserve for stability.
Not a good idea. The diode protects the circuits board from wrong polarity, so it should be kept in at all cost. Additionally, the voltage regulator needs one or two capacitors itself (for its input), and there’s nearly no room to integrate those on the fly. If you only want to have 12 V on the accessories pin, a small adapter board to accomodate the 7812 (that’s what you were thinking of, right?) would make more sense.
Cheers,
kuraasu
Well I have just ordered the parts to try this out, cost about £40. I haven’t made any circuits for about 20 years and will test my skills.
Problem I suffered was I was getting 24volts out of the head bed lead all the time regardless of any voltage present for the control side. I have found my photodiode thing (610) has a reverse flow on pins 3 and 4, if I connect these the other way round to the diagram its works like it should! Now all I need to do is make a new ‘final’ version to tidy up the mess left from trying to get it working.
[quote=“Moorron”]Well I have just ordered the parts to try this out, cost about £40. I haven’t made any circuits for about 20 years and will test my skills.
Problem I suffered was I was getting 24volts out of the head bed lead all the time regardless of any voltage present for the control side. I have found my photodiode thing (610) has a reverse flow on pins 3 and 4, if I connect these the other way round to the diagram its works like it should! Now all I need to do is make a new ‘final’ version to tidy up the mess left from trying to get it working.[/quote]
Sir,
Have an upvote from me!
It almost flew outside my window!
Had the same problem and saw in the datasheet then that pins 3 and 4 are switched from place 
and it works now!
Moorron
Indeed, the SFH610A (Vishay Semiconductors) optocoupler has a non standard pinout on pin 3&4. Please check that you really own a SFH610A-1 and check all connections on your circuit. If its any other type, the resistor values may be completely wrong and could cause an “always on state”. If you connect the other way, pin 3&4 swapped, you will probably notice no output at all, regardless of any input signal.
Edit: Note that the schematic sign does not represent the hardware pinout placement!
Sorry you are right, the diagram shows the correct wiring but the 610 chip has the pins the other way round. I should have seen this from the 610 info but ignored it. lesson learned
I had it wires to my K8200 today and it worked well, took less time to heat the bed than the hot end. Trying to print of some housings now to make it a nice fit.
Great mod.
Cheers
Andy
[quote=“Citystars”][quote=“Moorron”]Well I have just ordered the parts to try this out, cost about £40. I haven’t made any circuits for about 20 years and will test my skills.
Problem I suffered was I was getting 24volts out of the head bed lead all the time regardless of any voltage present for the control side. I have found my photodiode thing (610) has a reverse flow on pins 3 and 4, if I connect these the other way round to the diagram its works like it should! Now all I need to do is make a new ‘final’ version to tidy up the mess left from trying to get it working.[/quote]
Sir,
Have an upvote from me!
It almost flew outside my window!
Had the same problem and saw in the datasheet then that pins 3 and 4 are switched from place and it works now![/quote]
Made me check my wiring more than once, been 20 years since I did my college work on this stuff but got there in the end without any fires!
Glad I could help.
[quote=“rwang.me”]Hi guys,
Thank you for the information. I followed the first several pages, bought IRLR8743PBF and made a circuit. Then I realized that there exists a better solution. IRLR8743PBF only allows 30V which is too close to 24V. But the onboard MOSFET can go up to 70V. And I don’t feel good hangling wires and circuits around. So I changed to the following solution.
First I soldered one wire and two female connector to one 4-pin male connector.
Then I plugin the connector to the board. The heatbed goes to the new connector. The red wire goes to 24V+. The black wire goes from the PCB ground to 24V ground. That’s it. Simple and reliable.
It takes one to two minutes to heat up from 15C to 50C using 24V. The 24V 15A power supply I bought can adjust voltage from 20V to 30V. 24V gives the bed 90W power and probably 10W to the factory wires. The factory wires remain cold when heating up the bed. But I will replace them and boost the voltage to 30V, which will give the bed 150W power. Also I feel the need to increase the voltage of extruder. It’s too slow now.
The heatbed LED lights up using 15V power not the 24V power.[/quote]
Has anyone else tried this method?
I did order the components for the print from Edirol but i cant seem to get it working.
Off course that is because i am not so good with electronics, i can follow the lines but the correct placement of all the components is sometimes a bit of a ques.
If Rwang his option works and does not damage the board, this would be way more easy and cleaner.
If i understand correct I need to hook up the Ground wire to the standard 15 volt power supply negative and also connect it to the 24 volt supply negative.(bridge/connected them together)
The plus side of the 15 v power supply goes as normal to the board.
The plus side of the 24 v power supply goes to the plus side of the heatbed which would normally connect to the 15 out from the board.
I have a fan in the case which switches on at 40 c in the case.
[quote=“2stimpy”]
I did order the components for the print from Edirol but i cant seem to get it working.
Off course that is because i am not so good with electronics, i can follow the lines but the correct placement of all the components is sometimes a bit of a ques.[/quote]
What is the problem? There is also a PCB-Layout on page 5 of this thread.
[quote=“2stimpy”]
If Rwang his option works and does not damage the board, this would be way more easy and cleaner.
If i understand correct I need to hook up the Ground wire to the standard 15 volt power supply negative and also connect it to the 24 volt supply negative.(bridge/connected them together)
The plus side of the 15 v power supply goes as normal to the board.
The plus side of the 24 v power supply goes to the plus side of the heatbed which would normally connect to the 15 out from the board.[/quote]
AFAIK someone in here did this way and it seems to work but I do not guarantee.
