Show Off your PCB Projects

[bob345]

Like the title says, I think it would be nice to see some printed circuit board projects others may be working on that they are willing to share as there seem to be a good amount of people here that are really into electrical engineering. Anything from hand soldered perf-board projects to full blown PCB assemblies would be great to see here!

 

Here's a small test board i recently put together for a larger project. This board is for verification of a mixer that will likely be used in a wide band down converter for one of the stages. Being well into microwave territory, every detail of the pcb and layout can effect performance which is why microwave board layouts tend to look so different than conventional layout. Layout was done using kicad 5.0 and simulated with a combination of QUCS and Sonnet

[Hackentosher]

I don't have as much as I'd like after my first year of school, but here is a small 7805 and 2222 NPN on a board to power and operate a relay on a CNC router. The microcontroller can't supply enough current to drive a relay. The power for the 7805 came from the 24v DC power supply so that if the emergency switch was opened, the router motor would immediately shut down as the drive circuitry for the router relay would instantly de-energize. It's a good emergency stop. 

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Next is a current sensing board I designed for a project at work featuring a 3.3v meanwell power supply to power a microcontroller off of a 240v bus. It features a precision 500 u Ohm shunt, traces that are too small, no ground planes, and PCB mount XT60 connectors. I Have yet to verify if it works as thing after thing has gotten in the way. I need to double check my voltage divider and opamp feedback math, and solder on a bodge resistor. It's a bit of a mess, but it's the first PCB that I've ever gotten ordered so I'm proud of it. I learned a lot.

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 think my next project will be a 60% mechanical keyboard PCB, but I need to finish other personal projects before diving into another. My goal is to design something with a microcontroller on it, as my lab does a lot of their own custom microcontroller board designs, I think this would be a good project.

[Unimportant]

5 hours ago, bob345 said:

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Aggressive Lithium Ion series balance charger. Charges up to 4 Li-Ion cells in series no matter how unbalanced/different the batteries are:

 

Class D-Amplifier power stage prototype meant to mate with easily swappable PWM stage prototypes for development purposes:

This is the third iteration and I'm pretty stoked about the fact that this thing hardly radiates despite 15nS transistion times @ 50V upto 10A.

 

All my other PCB's I've currently on the bench are work related and not allowed to show

[Hackentosher]

13 hours ago, Unimportant said:

Aggressive Lithium Ion series balance charger. Charges up to 4 Li-Ion cells in series no matter how unbalanced/different the batteries are:

That's awesome, I usually end up using hobby LiPo chargers, which can throw a fit and are very slow to balance. I could use something like this.

[Unimportant]

19 hours ago, Hackentosher said:

That's awesome, I usually end up using hobby LiPo chargers, which can throw a fit and are very slow to balance. I could use something like this.

I've hundreds of second hand 18650 cells pulled from laptops, cordless drills, etc...

 

Their wear levels are all over the place and even tough I try to select cells that test at similar capacities to make a battery pack I find that most commercial balancer solutions simply refuse to charge such dissimilar cells.

 

So I designed this. It charges all the cells in series and each cell has a bypass transistor parallel to it (on the bottom of the board on a heatsink). The bypass transistor starts conducting at 4,15V and shunts the charging current around the cell, preventing it from going over 4,15V while the other cells continue charging. When all cells are bypassed the battery pack is full.

 

It also does not charge if any cell is below 2V unloaded (damaged cell safety) or reversed polarity.

[Faisal A]

[ShredBird]

@bob345 I wasn't expecting to see microwave design when I clicked this topic, then I saw your fenced in stripline. What bands are you working in? What type of connectors do to striplines terminate into? Judging by the standard 100 mil pitch headers for power this a pretty tiny board. Are C1, C2, C3 and L1 part of a matching network?

I'm an RF/Microwave engineer myself so I'm sure there is plenty we could chat about.

[bob345]

16 minutes ago, ShredBird said:

@bob345 I wasn't expecting to see microwave design when I clicked this topic, then I saw your fenced in stripline. What bands are you working in? What type of connectors do to striplines terminate into? Judging by the standard 100 mil pitch headers for power this a pretty tiny board. Are C1, C2, C3 and L1 part of a matching network?

I'm an RF/Microwave engineer myself so I'm sure there is plenty we could chat about.

The connectors used are 2.92mm connectors. A bit over kill for this, but i have a bunch of them and they are solder less so why not. the L's and C's you see are really only there as bias tees as this mixer has a built in LO amplifier and if amplifier. Nothing too crazy going on, just breaking out the chip really. And yes, the board is quite small. here are a few images. Mixer is in a 4x4mm qfn and the small passives are 0402'. Mixer is good for 2-7.5ghz

[Hackentosher]

This is a subproject for the lab I work at. It's my second PCB ever, and it's an implementation of a pretty high frequency boost converter IC, with a cutout for a (relatively) bigass LED COB, and a FET for fan control. Unlike my first board, this one (mostly) works, I'm just having some funky issues with the fan control, but I may be able to work around it with some bodge wires.

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This LED is something like 2000 lumens so even the reflection off your hand will burn holes in your vision. It's going into a system aimed at improving campus security, and I think that's about all I can say  

 

[bob345]

On 9/22/2019 at 12:54 PM, Hackentosher said:

This is a subproject for the lab I work at. It's my second PCB ever, and it's an implementation of a pretty high frequency boost converter IC, with a cutout for a (relatively) bigass LED COB, and a FET for fan control. Unlike my first board, this one (mostly) works, I'm just having some funky issues with the fan control, but I may be able to work around it with some bodge wires.

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This LED is something like 2000 lumens so even the reflection off your hand will burn holes in your vision. It's going into a system aimed at improving campus security, and I think that's about all I can say  

 

Nice looking layout! One thing i would recommend though is leaving solder mask over via's that get close to pads as they can cause issues with assembly. Via's in pad like in D3 can cause manufacturing issues as well as it can wick away the solder paste. Not much of an issue for manual assembly, but definitely can cause a headache during volume manufacturing              

[Hackentosher]

47 minutes ago, bob345 said:

Nice looking layout! One thing i would recommend though is leaving solder mask over via's that get close to pads as they can cause issues with assembly. Via's in pad like in D3 can cause manufacturing issues as well as it can wick away the solder paste. Not much of an issue for manual assembly, but definitely can cause a headache during volume manufacturing              

Thank you!

 

That's a good tip, I'll keep that in mind. Fortunately this board will never be brought to mass production, so I'm not too worried about solder paste wicking. A lot of the vias that are close to pads are connected to those pads themselves, so I don't think that's an issue, but I'll double check the schematic before we order rev 1.1.

[bob345]

Threw together a little headphone amplifier to try out osh parks new after dark option that gives you a 2 layer board with black fr4 and a clear soldermask. Looks pretty sweet if you ask me. Design is based on a tpa6120 so it should perform decently once i get the parts in. Might try my hand at a full amp/dac if it works out well.