Making a PCB?

[KD6HQ]

I am considering making my own accessory PCB. Normally I would just breadboard something like this but this time I'm considering carrying more current than I normally do. Since I've never done this before I was wondering how wide the traces should be to carry 12V DC at 5A, 11A and 15A. Various components on the board will include: relays, voltage divider, fuses, fans and lights. This is just an idea of what I want on it, as there may be more components. Anyway does some one have suggested trace widths?

thank you

[thawkins]

[KD6HQ]

thawkins

thanks for the help

kd6hq

[KD6HQ]

Preliminary


J1 - 12V DC, 3A input, power JP1
J2 - 12V DC, 15A input Power +
J3 - 12V DC, 15A output to Printer board V. input
J4 - 12V DC GND Return from Printer Board
J5 - 12V DC GND Return to power supply
J6 - 12V DC, 15A input Power +
J7 - 12V DC, 15A output to Bed Heater board V. input
J8 - 12V DC GND Return to power supply
J9 - 12V DC GND Return from Heater board

The calculator that I used estimated that the circuit trace need to be about 6.29 mm wide.
So I had to use two pins on the connector otherwise they touched each other.

JP1 - 15 pin pair for auxiliary connections. Fans, lights etc. Total current is limited to 3A.
JP2 - Connects to a remote switch to turn the 3A circuit on and off.
JP3 - Connects to a remote switch to turn the Printer power on and off.
JP4 - Connect to the remote bed heater connector on the printer board. *******
***** You must observe polarity ********

[Mooselake]

Let me know when you order some boards; I'm willing to buy one from you.

Consider adding a few LEDs for input and output power indicators for the bed, board power, etc. It's hard to have too many LEDs. Also maybe the relay holes should be slots so you can solder in a car relay, or at least bigger holes so you can solder in some and make a cheap relay socket. They work for blade fuse holders, too.

Kirk

[KD6HQ]

Well I did some looking around today and found something that might work a little better.

I found the following connectors. This would allow for the use of automotive fuses and relays. Although I like the idea of having the relay on the PCB, I think this would save some room on the board. I'll do a layout and see how it goes. Check back in a day or two.

[KD6HQ]

In this version (C) the following components have been removed.
20 A relays
Protection diodes for relays
Connector from the printer board to the heater relay
AG3 type fuse

Added
3 led's indicating power is turned on.
The fuses are not Panel Mount type.

As you can see several of the "panel mount connectors" have been added.
If no other components are added, then this board could be relayed out to reduce size even more (80x100mm).

Since the relays for the heater bed and main power to the printer board have been removed access to the output side of the relays is no longer available. So led's could not be added to indicate when relay was in use. Since the coil protection diode has been removed, I would recommend purchase of relays that have the coil protection diode built in.

In order to keep the trace width of the 20A relay connections down it will be necessary to use a little heaver copper board. The normal is 1oz., but 1.5oz or even 2.5oz is better.
At 1oz. the trace is estimated at 18.7mm, 1.5 is 12.5 and 2.5 it 7.49 mm. These sizes are based on a 1" long trace. Reducing the trace to a length of 1/2" did not make any difference in calculations.

[KD6HQ]

Although it was fun playing with this software, the quote I got prevents me from making any. The quote for 2 prototype boards was $88, and that did not include shipping. Time to get the breadboard out.

[Vapor]

Is it a 2 layer boards?

If so, you could make one by yourself.

[thawkins]

[2Mylent]

Otherwise, as I am always with good black marker and Iron Perchloride.
- We have traced the circuit on the PCB and then the drawing board with a good black marker.
Finally, dip the PCB in the Iron Perchloride leaving only copper tracks on the circuit.

- Instead of black marker, special stickers can be used for PCB (selling electronics store). Dip the PCB in the Perchloride.

- Finally, the top, buy a photosensitive PCB and Print circuit on a layer laser printer and expose the cuicuit UV. Dip the PCB in the Perchloride.

- For double-sided circuit, I begin by drawing a face, and then I do the drill holes and only after I draw the second side.

[Vapor]

You can PM me if you would want to pursure this. I have some experience doing this. I used to manage an aerospace electronics factory. We built things that go on the 787 and global hawk uav's.


There are the little stickers that you can "rub on" and etch it. You could use toner transfer, or other methods. It depends upon how bad you want it.

Then you'll have to drill the holes. It might be a pita.

There are other places you can go for cheap prototype boards to have them built.

PM me and we can talk about your needs and get you something that will work.

[KD6HQ]

Lots of options here. Have to do some more thinking, since this is my 2nd printer I'm in no hurry.

Vapor - I will.

[KD6HQ]

Just happen to run across this in E-bay.... http://www.ebay.com/itm/271543985231?_t ... EBIDX%3AIT

[Mooselake]

That looks pretty similar to Traumflag's . Found a of similar products in the Google shop.

I still think yours is more better.

Kirk

[KD6HQ]

It's taken a while now but I finally got around to making my own PCB.
This is what I call "Printer Accessory Board Rev. "A" and although it works
I am not 100% happy with it yet and there will be a Rev. "B". I'm in a position
where I use my power supplies for other devices other than the 3D printer. This
led me to include an "On/Off" switch so the power supply can be on but the printer
will not necessarily be powered up.
As seen on the Picture.
#1 - 12V DC 3A. input. This connector provides power thru the On/Off switch to power the 15 dual pin
accessory plug and power to the printer.
#2 - 12V DC 11A. input. This provides printer power thru relay "B".
#3 - 12V DC 11A output to the printer.
#4 - 12V DC 15A input for the heated bed thru relay "C".
#5 - 12V DC 15A output to the heated bed.
#6 - Inductive coupler connection. Separate circuit for the inductive coupler as suggested by Printrbot.
#7 - Up to 15 attachments such as fans and light can be connected. Two pins to each connection.
However there is a total current limit of 3A. So you must total up how much current is used by
each device so you do not exceed the 3A limit.

Notes: Each relay has a diode across the coil to help provide protection to other circuits.
You can't see it in this picture but relay "C" has a 2 pin connector to be connected to the heated bed
control circuit on your main printer board. This allows for normally control of the heated bed by the printer.

LED's have been added to show were power has been applied. For instance when you apply power (12V DC 15A)
to #4, led "L1" will light up. When the printer turns the heat bed on, led "L2" will light up showing power is
being applied to the heat bed.

In this picture at #6 note that I did not have any 3-pin connectors but the holes are there.

The blue connectors ( 1-5) are rated at 15A.

This is made on a 3 Oz. single sided pcb.

[Mooselake]

Need a beta tester?

Kirk

[KD6HQ]

Kirk

PM sent.

Don, kd6hq

[KD6HQ]

Hello RetireeJay

A little guidance please.

On my "Printer Accessory Board" (seen above) I have a couple of things I would like to change.
One is to add a Polarity Protection components so that when the power supplies are plugged the rest
of the circuits are protected before put into use. I believe I can do this by putting a Diode
across the input terminals. 12V @3A, 12V @ 11A and 12V @ 15A.

Questions:
1. Is the diode alone enough to do this?
2. How do you pick a diode to use? I know to use a 12V diode but I'm not sure about any of the other
specifications.
3. Can you think of any questions that I should be asking but am not?

thank you

Don

[RetireeJay]

Don,

It looks like your schematic already shows diodes in place. You have them wired in series with the supplies. That's OK, but be aware that you will suffer a voltage drop of at least 0.6V if you are using standard diodes (Schottky diodes have a smaller forward voltage drop). In other words, if your supply is 12V, you will only deliver 11V or so to your loads. By the way, diodes that can handle 15 Amps are not your everyday diodes in glass or plastic cases; they would need to be metal cased ones with studs to be mounted on heat sinks. And don't scrimp; for a 15 amp circuit, use a 20Amp diode or larger. The voltage rating will almost certainly be larger than 12V, and that's good. It doesn't matter very much as long as it's greater than 12V.

If you want to put diodes in parallel with your supplies, then that's called a "crowbar" circuit. If the power supply is hooked up with the wrong polarity, the idea is that the diode will short-circuit the supply and prevent harmful reverse voltage from reaching your load. But be aware that the diode and the supply both will be severely stressed when this happens, and you could end up releasing the magic smoke if the supply doesn't protect itself well enough and fast enough.

Another approach might be to have green LED's that light up when the voltage has the right polarity, and red ones that light up when the voltage has the wrong polarity. There are two-in-one packages that do this, so you wouldn't have to re-design your board.

Of course, you don't need to be concerned about the polarity of voltage applied to resistive loads like heated beds and cartridge heaters on extruders.

[KD6HQ]

Thank you RJ.

Since this revision has not been built yet, and the board layout not modified,
I think I will delete the diodes and just use the LED method. Visually simpler and
all I have to do is change a couple of part numbers for the LED's.

[veng]

You could add the crowbar diodes and a PTC.

[KD6HQ]

For those whom may be interested I've finally completed my relay board.

It has 4 circuits on it.
1. Auxiliary devices (fans, led's etc.)
2. Power to RAMPS 1.4 / Arduino 2560 board
3. Power for heated bed using automotive type relay or ?.
4. Proximity Sensor voltage divider if you need it.

So far I have only tested circuits 1 and 2, they are working as expected.
Since I'm in the middle of building the printer, circuits 3 and 4 have not been tested yet but I suspect they will work.

The board is make from a single sided 3 Oz. copper board.
Circuit 1 - 12V at 5 amps.
Circuit 2 - 12V at 15 amps.
Circuit 3 - 12 V at 20 amps.
Circuit 4 - 12V at les than 1 amp.

Along the way I've gotten side tracked several times. I had originally wanted to use this with my modified Printrbot Simple Makers kit. Some where along the say I decided to use a RAMPS 1.4 / Arduino 2560 board set, making a 12 x 8 x 12 printer using the design of "Jonbot Plus - a new fully printed printer!" by "orangefurball" which is in process now. Along the way I've modified a display design to include a remote on/off switch and a voltmeter, which monitors the supply voltage to the RAMPS/Arduino and relay boards.

Current capacity of the traces on the board were calculated using "Trace Width Website Calculator" found here http://www.4pcb.com/trace-width-calculator.html .

Circuit 1 has a 2 x 15 pin connector. This means that you can connect up to 15 12-volt accessory devices such as fans, led lights etc. However the total current of the devices cannot add up to more than 5A total. The circuit trace can't handle any more.

Appropriate capacity fuses protect circuit 1,2 and 3. However you must observe polarity when hooking up a device.

Eagle Software (ver. 7.3.0) was used in the schematic and PCB design.

[LulaNord]

Hi...i am new here. As per my knowledge you should consider adding a few LEDs for input and output power indicators for the bed, board power, etc. It's hard to have too many LEDs. Also maybe the relay holes should be slots so you can solder in a car relay, or at least bigger holes so you can solder in some connectors and make a cheap relay socket.

[KD6HQ]

Actually the Leeds for the bed are there, the bed was not active when the picture was taken. If you look at the schematic they are indicated by L5 & L6.
The LED's that are lit up, 1 shows 12V @5A, 1 for 12V@12A, then the other show up when the 12Vs is connected to the circuit. So all theelads you speak of are already there.

As far as the car relay goes, I would not recommend using car relay. Most of them are mechanical relays and were not met for rapid switching. They have been known to overheat and fail during operation. If I were designing the board today I would use a MOSFET setup, they are much more reliable for this purpose. They also can be purchased separately on e-bay and ready to use. http://www.ebay.com/itm/3D-Printer-Heat ... SwFwpXcarE

If you do decide to use the auto relay, make sure you de-select the PID switching in the firmware. Look for a line something like this #define PIDTEMPBED. By committing out this line the firmware will use "Bang Bang" switching and the relay switching rate will slowdown considerably.

Thank you for the commits.

[Mooselake]

If you're willing to wait for the slow boat delivery you can order it and save about 5 bucks (US).

Kirk

[KD6HQ]

Hi Kirk, that's not bad, I was not willing to wait though. I've put one in a new CoreXY. It's pulling about 22 A and is not even breathing hard.