Help design a simple breakout board

[mstc]

I think the main attraction of going with JLCPCB was 1) they have a fully integrated design app that allows direct ordering and 2) they do the assembly for you. My original intention was to find an easy soldering solution for these plugs, and having to solder/bake the SMD plugs myself probably would have defeated the purpose.
Of course the price was very attractive too. Final all in price - boards, components, assembly and DHL shipping came out to $11 per big board (one big board has 14 smaller boards - 1x LDO board, 2x mosfet boards, 2x LED boards, and 9x breakout boards - so it works out to less than a $1 per small board).

I went with the 1.6mm PCB as that was the default option, they also have 0.8 and probably would have been wiser to go with that (should have just measured an AIO for pcb/pad size instead of being lazy). They also have the 2oz option, but that costs quite a bit more and I didn't think it was needed (it added more than $30 to the order).

@Lemony if you still want to help test some, just send me a pm.

[voodoo614]

A band saw probably would have cut theses pretty well.

[mstc]

A band saw probably would have cut theses pretty well.

Yup that was the first tool of choice that came to mind, but too bad I don't have access to one anymore.
It probably would have been easy scoring/snapping if it was an 0.8mm board.

[voodoo614]

Yup that was the first tool of choice that came to mind, but too bad I don't have access to one anymore.
It probably would have been easy scoring/snapping if it was an 0.8mm board.

So they wanted to charge you more to add slots. How much was the difference in price?

[mstc]

My first few submissions was with slots, but because it had to go through the components assembly there were certain requirements to make sure the board was strong enough and I had to revise the slot placement several times. But on the last revision they mentioned that it was multiple designs and would have a surcharge (I think it depends on the tech reviewing the design). I forget exactly, but probably added more than $40? which was nearly double) and at that point I just wanted to get the order done so removed all the slots to pass as one design.

[iFly4rotors]

Hi Mstc,

Yeah, I am late to the party.  Very interesting. 

I like it.    Especially the Mosfet switch, very cool 

Later, iFly  

[mstc]

I purchased some 2.7mm wide 5v COB LED strips which draw around 600ma per meter. I wanted a switch to turn them on/off, very similar to what Betafpv provides with their COB LED set, but didn't find any that compact. I decided to just have them made instead as the price of a custom assembled PCB is relatively reasonable. The total cost to print the boards, purchase the components, have them soldered on, and shipped came to $27 for 5 sets of boards. On each board, I had two switches and two breakout boards, so that works out to $2.70 for one switch and one breakout board.
I guess if you are comfortable baking on your own SMD components, you could save $20.

I probably should have prototyped the circuit, but I did not have a spare mosfet on hand, so hopefully the design works. If not at least I'll still have the breakout boards. I went with a board thickness of 0.8mm this time, last time the 1.6mm was too thick, this should make them easier to cut apart as well.



After I submitted the order, I found my Betafpv switch. It actually has the plug installed on the back side, and uses much smaller resistors so overall is more compact. I guess I was worried to go with the smaller resistors as they had such low mw ratings, and probably didn't need to space out components so much.



Anyways, the boards have been made. JLCPCB gives you a blow-by-blow update of the progress. The production took 2 days to complete. I was cheap and went with the $2 shipping option, so hopefully the boards will arrive in two weeks.

[skywanderer]

I purchased some 2.7mm wide 5v COB LED strips...

Those COB LEDs are amazing huh! What color are you using? Honestly hadn't thought of using them on kwardkarpters but how are you using them here, curious?

[mstc]

The strips themselves are quite inexpensive, around $3/m, so I grabbed some to play with (white, ice blue, purple, and rainbow - but they also come in red, pink, green, yellow, orange, deep blue, etc...). Was thinking to start on the 2.5" cinewhoop as the ducts make a nice mounting surface (that seems to be the fad), but want to wrap one of the larger open prop setups too. The rainbow strip does require a controller (like the one Speedybee sells), I was thinking just to add on a ESP32 or maybe a simple ATTiny85 for some custom effects.

[mstc]

Well the boards arrived today, took two weeks, but I guess that's what you get for $2 shipping. The boards were very small compared to the first batch, smaller footprints and also cramming less mini boards on each one. The 0.8mm thick PCBs were much easier to cut apart than the 1.6mm boards. Just some a quick sawing with a jewelry saw, or scoring the board and snapping also worked.

The two old v1 boards on the left for comparison. The v2s definitely a lot more compact. The breakout board is just a hair wider than the plug itself and soldering was very easy even with the tiny pads.



For the mosfet switch, I used a N-MOSFET (AP3404S) which is rated up to 30v, 6.5A continuous, and has a threshold voltage of 1.6v (turn on voltage). I also added a gate resistor to protect any MCU pin. There was a little anxiety as I never protoed the circuit, but fortunately it worked just fine. Switching on only when a positive voltage is applied to the gate pin.

Here it is powering a 2m led strip, drawing 1.1A at 5v with no heating up after several minutes.



I've also been testing the addressable LED strip (rainbow or neopixels), but I guess I didn't realize the pixel density of these newer strips - the ones I have claim 160 and 200 leds per meter. Unfortunately the MCUs I planned to use (ATTiny85 or ESP32) does not have enough memory to handle so many LEDS as each pixel needs 3 bytes of RAM. However the SAMD21 MCU comes with enough RAM to drive more than a thousand pixels (32k RAM!!) so would be a better choice. It is another inexpensive MCU with many dev board options but I didn't have any on hand, so I ordered some of these as this version seems to have the smallest form factor. It comes with 4 pixels on the board and no signal pad, but assume I can piggy back off one of the pixels.

[mstc]

I received the Neo Trinkey board. Apparently Adafruit has several different versions of this board, all with the same MCU. It also comes with the option to use CircuitPython, which is a nice for anyone not wanting to use the Arduino IDE. The board plugs in as a USB drive, you simply copy your python script to the drive and voila, the code runs immediately.

The board works fine and drives around 400 pixels I connected. The LED strip is wired to the last DATA OUT pin of the last onboard pixel. That is the lower left pin or the lower left pixel. I guess the LED casing was a little soft, I partially melted it with my soldering iron, but it was fine. For ground there are several points you can connect to, I chose the bottom of one of the caps.
The 4 onboard pixels are powered by the 3.3v regulator, but for the strip of several hundred pixels I used a separate 5v supply.



I have two different strips, the top one has a 200 led/m density compared to the bottom one of 160 led/m. I believe the SpeedyBee strip is 160 led/m.



For anyone wanting to make their own custom LED effects, this board should be a good option.
The board is $7, and the led strips range from $5-9 per meter (lower density costs less).

[ph2t]

That looks mad! I'm looking to make my led switcher smaller and lighter with a goal to use it on small whoops. I fly a lot in the evenings out in the garage and down the driveway so a bit of extra light goes a long way.

[mstc]

For the single color LED strips, the tiny mosfet board works fine, or if you can do micro soldering, just solder on a mosfet and resistor to the wire for the most compact footprint.

I guess it doesn't show in my photo, but the neopixel or rainbow strips (WS2812 leds) can be individually controlled and require a MCU to command each pixel, otherwise they will not light up. They are great for animated effects such as cylon eyes, pulsing/waves/streaking, as well as lighting different parts of the drone in different colors with a single strip (flame effect in the rear, headlights in the front, flashing blue/red siren on the side), light speed streaking, disco ball flashing, indicator bar, star twinkling, spot fade in/out, or whatever eye candy you can imagine.