I would like to have a go at building the upgrade but I am getting a little lost following all the comments and variations.
Does anyone have (or would be willing to put together) a concise guide on building this board - schematic, board layout and parts list?
Sorry if that sounds like I am being lazy (clearly some of you have built the board with the information available) but I have a limited knowledge of building circuit boards and I want to make sure I order exactly the right bits (no bits with pins reversed for example).
Many thanks to all for the great input though. The heating time for heated bed is one of my biggest frustrations with the K8200 and I am hoping this will resolve it.
Regards
Peter[/quote]
+1
I think I almost did every upgrade I can do to my printer. I really want to start experimenting with ABS but my bed does not reach the temperatures needed for ABS. And heating up to 50 °C for PLA takes forever when I use a mirror. A tutorial on how to upgrade the heated bed would indeed be very handy!
I finally got myself to ordering a new power supply to get proper bed temperatures after struggling with printing out a few ABS parts using the stock configuration. (I ended up using blue painters tape soaked in ABS slurry on bed at 70 C which sort of works but lifts the tape off of the bed in the corners. The print is still fixed to the bed and completes properly, but in short: it’s a mess.)
At first i planned on getting the SNT MW100-24 which a lot of people seem to be using. I however ended up ordering it’s beefed up sibling, the SNT MW-SP320-24. This out of a few reasons:
[ul]
[li]Since the bed seems to need close to 100 W for maximum heating, I kinda like not being close to the supply’s max spec. Having about 200 extra Watts feels nice.[/li]
[li]My home is littered with cats and small children, so the more sealed up enclosure of the SP320 feels better from a safety stand point. (Adding a tweaked version of this cover to hide the live terminals makes it sort of complete.)[/li]
[li]The SP320 comes with a pre mounted temperature controlled fan, so I don’t have to worry about cooling.[/li][/ul]
Regarding the rest of the circuit, a few pages back, chris101 asked for alternate MOSFETs since the IRLR8743 seemed to be hard to acquire in Denmark. I myself live in Sweden and found out that Reichelt sells the IRLU8743, and they definitely ship to all of Europe.
Continuing on the discussion a few pages back about powering the 3drag main board directly with 24 V, I have a different solution in mind to which I would like some input. Since a lot of components, like the official LED ring, Stand alone controller, fan and so on use the raw input voltage of 15 V, I would suspect 24 V would cause a bit of overpowering problems there even if the board will last, albeit running really warm.
What if you constructed a 15 V voltage regulator circuit based on LM350, and powered the main board with that from the above power supply? As I can tell from the regulator’s data sheet (particularly from the top right graph on page 3) an input-output difference in voltage of 9 V (regulated 15 V on 24 V supply) allows for approximately 4.5 A current limit. As specified in the introduction of the 3drag main board …
… with the heated plate connected to a different power supply, we would only use approximately 2.5 A for heating the extruder leaving about 2 A of head room for the steppers and electronics. I couldn’t easily find any info whether this is sufficient, but I suspect it should be.
This setup would be really good for me, powering the entire setup from a professional and overpowered power supply, eliminating the need of having two supplies. (I have had problems with the printer locking up and ruining prints when my four years old plays with the spot light connected to neighboring power socket, and also once when disconnecting a powered on soldering iron in the neighboring socket. I suspect that’s due to brown out due to quick variations in voltage, which shouldn’t be in place in the SP320 since it’s both overpowered and filtered.)
I presume that includes the power loss of the (near-idle) supplies? The board itself should use about 1 W in that situation (not counting possible peripherals or accessories, of course).
[quote=“magu”]28 to 35 W on 15 V means approximately 2 A, which in turn means that the LM350 will suffice; woohoo!
[/quote]
keep in mind that the motor drivers produce lots and lots of load transients. Probably installing the maximum output capacitance mentioned in the app notes (100 µF) would be a good idea.
maximum output capacitance and a LARGE heat sink and even then it will probably work only for a few seconds until the linear regulator shuts down due to over temperature
24 Vin - 15Vout = 9V
9V * 2A = 18W
standard heat sink 20K/W -> 400°C way to hot
better try a LM2596 or similar switch mode voltage regulator module for this type of application
[quote=“motoritz”]maximum output capacitance and a LARGE heat sink and even then it will probably work only for a few seconds until the linear regulator shuts down due to over temperature
24 Vin - 15Vout = 9V
9V * 2A = 18W
standard heat sink 20K/W -> 400°C way to hot
better try a LM2596 or similar switch mode voltage regulator module for this type of application[/quote]
Thank you! You probably just saved me a lot of headache (and burnt fingers). Does it show that my baseline electronics knowledge is only from high school? =)
Funnily though, it turns out I actually have a ready made circuit based on LM2596 lying in my big-box-of-many-things™, which I bought for another project and have since forgotten about. (And also, I didn’t really read up on that particular regulator; I just used it.) The specs on the store page for the module says max 2 A (appears to be a HCJ-IPM-V2), but according to the datasheet for the regulator it should handle a standard current of 3 A with peaks of up to 4.5 A just fine; I suppose?
It also depends on the module’s other components what max current it can handle. The modules I saw were all rated for at least 3A I think. If you have it already in your box you can of course take a multimeter and measure the current with a dummy load.
I haven’t got the power supply yet. Will probably arrive by Wednesday or Thursday. I’ll probably just wire it up and give it a spin. Since testing seems to suggest that the board itself actually can handle 24 V I could ramp the voltage up a few volts above 15 if the amps are insufficient. Will just have to try …
Would anyone be able to help me troubleshoot the circuit board for switching 24V?
I have built the board as per instructions and diagrams earlier in this thread. The only component that is not exactly the same is the MOSFET, I had to get an IRLU8743PBF, but I think the spec is close enough (please correct me if I am wrong).
I have checked for shorts and cannot find any.
I have 1.9v across pin 1 and 2 on the Opto-coupler when 15v input is switched on (from control board). I assume that is about right for the LED in the Opto-coupler?
However, I have permanent 24V at the output to the heated bed, irrespective of whether the 15V is on or off.
I have tried measuring the resistance across pins 3 and 4 of the Opto-coupler but I am assuming as it is a transistor this is not going to give me a sensible reading? I am now at a bit of a loss to work out what is wrong.
[quote=“etlprws”]Looks like I have the wrong Opto-coupler. I have a SFH618A.
Can anyone advise if this can be made to work with different resistors or should I just forget it and get the SFH610A?
If it can be made to work some guidance on resistor values would be helpful as I can build circuits but I can’t design them!
Many thanks
Peter[/quote]
First, make sure you have connected the pins on the output side of the coupler properly. The circuit diagram and your coupler is not the same. Check out the datasheet and compare it to the circuit scheme
Sorry, I should have done a bit more research before posting.
As you say Magu, the SFH618A has pins 3 and 4 reversed.
I have swapped these over, which was surprisingly easy (swap wire link and resistor) and I now have a working 24V supply that switches on and off with the control board 15V input.
Thanks Magu and to all that have input to this thread…most helpful.
Got my setup working now, and damn it heats up quick. Also reaching 100 C is a first … will make printing ABS a whole lot simpler.
Regarding powering the main board through a HCJ-IPM-V2; well, it only partially worked. Heating the extruder to 220 C and moving around X and Y axis at the same time worked fine with a current of approximately 2,6 A, making the unit get quite hot (but not scorching hot). As soon as Z axis movement was added though, and the stepper started grinding, the regulator failed and the printer brown out:ed. It might be possible to add a beefy capacitor after the unit to compensate for the Z steppers gluttonous needs, but for now I just keep the original supply in tandem with the 24 V one for the heat bed.
When ordering a new heatbed I noted that at least reprap.me has a ready made power expander circuit for sale. I haven’t got a clue how it looks or performs, but it seems like it’s more or less the same as our home made circuits. Could be an alternative for people not comfortable building the coupler-mosfet circuit for themselves.
When ordering a new heatbed I noted that at least reprap.me has a ready made power expander circuit for sale. I haven’t got a clue how it looks or performs, but it seems like it’s more or less the same as our home made circuits. Could be an alternative for people not comfortable building the coupler-mosfet circuit for themselves.[/quote]
Thanks for this update. I’m really considering to order it. It’s not that expensive… Which power supply are most people using? I’ll still have to order that
