Building a Unique USB Card Reader: From Idea to Prototype

[@hexefx]

Current limiter: 1. Better check the dropout voltage the LM317 will be introducing. Add 1.2V drop on the current limiting resistor to it. 2. The full output current passes through the current limiting resistor. Can the digital pot chip handle it? 4.4mA is the max wiper current according to the datasheet. 3. 10k 100 step pot for a range which requires hundred of ohms? Iout = 1.2V/Rlimit, for 500mA Rlimit=2.4Ohm So, if it really has to be LM317, i'd boost the 5V to compensate the drop and add a stepper motor controlling a high wattage wire wound potentiometer (plus a steampunk enclosure) :) Or just use one of the hundreds of dedicated USB power switches with adjustable current limit. They will work with digital pots, have a very small burden voltage plus a few more protections built in.

[@MAYERMAKES]

and those would be great ideas for a second version!

[@hexefx]

@@MAYERMAKES Here's another one, using the same type current limited power switch: make an inrush current limiter (ie.: set the input current to 100mA initially for the enumeration time and after some delay to max allowed value). This will allow a lot more capacitance on VBUS and more stable operation. For the output protection - there is an interesting chip, UCS3205, have it on one of my boards now, although not tested yet. It combines all the required functions in one: power switch, current limit, overcurrent/voltage protection and it has a voltage output proportional to the output current, no need for any external sensing.

[@philhutchinson7849]

That was really fun Clem! Thanks for showcasing the process and reasoning.

[@MAYERMAKES]

your are welcome

[@renegaed]

This was an extremely inspiring video to watch. Often times my first prototype doesn't work as intended and i get very frustrated, but seeing someone as experienced as yourself going through your own set of issues is really encouraging that this is typical of the process itself.

[@MAYERMAKES]

that was the point i wanted to get across, there will seldom be a prototype without flaws and everyone gets through the same process. as the projects get more comples the troubles get more complicated but it is still the same proces and solving these troubles alos follows the same procedure.

[@renegaed]

@@MAYERMAKES Thank you for showing that

[@MAYERMAKES]

Sometimes the hardships along the way are muc hmore interesting than the outcome! share your overcoming project trouble stories!

[@964tractorboy]

Like your project videos a lot even though I'm very new to them. Lots of good tips, so thanks for taking the time to do so!

[@MAYERMAKES]

You are welcome 😂

[@cdyoutoob]

For your LM317-TO-220 you could select(or place) and type Y which flips vertically allow your to run wire in more logical fashion

[@MAYERMAKES]

Good idea, alternativelly there is also a "bottom side up" to220 footprint in the kicad libs!

[@gentlemanhk]

Great! I like this episode!

[@MAYERMAKES]

Thanks

[@nesbionics]

It's true!!!, you don't have to invent the wheel, but you have to master the technology, if you don't do that, making a change in the prototype will take you a long time, regards

[@MAYERMAKES]

thanks!

[@raguaviva]

amazing video, please keep them like this :)

[@MAYERMAKES]

Thx😂

[@raguaviva]

@@MAYERMAKES BTW there is a big need to power ESP32 using lipo batteries, the problem is that we still don't have a good solution, may be you would like to take on this challenge and help people out? :)

[@MAYERMAKES]

Oh i have a few, its noted for the next episode

[@ergindemir7366]

Since you use esp32 you could make wifi card reader, especially useful for Apple users without usb nor card reader.

[@MAYERMAKES]

Yes, and also the chip on board has BLE so configurations could happen from phones or other computers on the network. I think you perfectly understood the idea of iterating on a product as discribed in the video!

[@dethfactor]

What is the PCB can shaped clamp / board holder and light? I've never see one in that style.

[@MAYERMAKES]

The miami vise stl by atomic14 and an endoscope cam

[@Kysen10]

I had that exact same reflow issue with the ESP32 C3 module. The pads just don't like the solder at all.

[@MAYERMAKES]

I soldered it multiple times befire ,butvit is very particular on heat and the shirld sucjs up a lot of it. Very easy to go wrong😂

[@TheEmbeddedHobbyist]

Nice video, but you could have pointed out all the certification issues that need to be addressed if you want to sell your final product.

[@MAYERMAKES]

I could have, but that would also make a great dedicated video topic. as Certification in the first prototype or POC stage is not the core concern i did leave it out to not overcomplicate things. But we might do a dedicated video on EMc and other certifications.

[@TheEmbeddedHobbyist]

@@MAYERMAKES would be a good idea, as a lot of folk seem to think that certification does not apply to them selling on the usual sites. EMC should be considered in the board layout stage as track layout can make a big deal. EMC can be a pain but I think RED if you have wifi is a real pain,

[@DiyintheGhetto]

Clem one thing about the metal case. It might block a lot of the wifi signal coming from the Esp32. I'm just thinking outloud here.

[@MAYERMAKES]

that is a detail i did not explicitly mention in the video but you can see it in many shots, the antenna is sticking out the back of the device. the usb-c ports are exactly in line with the end of the case, but the antenna goes further back so it is not blocked by the case.

[@DiyintheGhetto]

@@MAYERMAKES Honestly I didn't see the antenna sticking out the back of the case. I missed that part. I have to rewatch it again. Thank you.

[@MAYERMAKES]

​@@DiyintheGhettoit is easy to miss since i did not point itvout explicitly😂

[@ThomasFranksomt]

I figured three boards were a minimum order!

[@zaprodk]

You are running the USB-lines just under the crystal with no groundplane inbetween. That's a big no-no.

[@MAYERMAKES]

While a big non no, the lines run next to the crystal not directly under it. @6:47

[@ddjazz]

there were no problems with your board only challenges :D

[@MAYERMAKES]

thats agood way to put it!