Mini portable power supply DIY

Here is a small DIY project, for a portable/bench-top power supply. We are not aiming for the best regulation, neither most power. But portability and bench-top estate optimisation.

This is based on the famous DPS3005 (about 25€)

Let’s 3D print an enclosure, found on Thingiverse:

And grab all the jelly beans needed:

Wire/crimp/solder:

Does work quite well:

With not much noise (static 100mA load):

And as I’ve this fancy portable solder iron with a bunch of li-ion cell:

It works on the road!

Plastic part surface finish: please stop making mirror products

They are simply dust, fingerprint and scratch magnet, everything is summarised in the amazing book The Hardware Hacker: Adventures in Making and Breaking Hardware from Andrew ‘bunnie’ Huang

“My world is full of small frustrations like this. For example, most customers perceive plastics with a mirror finish to be of a higher quality than those with a satin finish. There is no functional difference between the two plastics’ structural performance, but making something with a mirror finish takes a lot more effort. The injection-molding tools must be pains-takingly and meticulously polished, and at every step in the factory, workers must wear white gloves. Mountains of plastic are scrapped for hairline defects, and extra films of plastic are placed over mirror surfaces to protect them during shipping. For all that effort, for all that waste, what’s the first thing users do? They put their dirty fingerprints all over the mirror finish. Within a minute of a product coming out of the box, all that effort is undone. Or worse yet, the user leaves the protective film on, resulting in a net worse cosmetic effect than a satin finish. Contrast this to satin-finished plastic. Satin finishes don’t require protective films, are easier for workers and users to handle, last longer, and have much better yields. In the user’s hands, they hide small scratches, fingerprints, and bits of dust. Arguably, the satin finish offers a better long-term customer experience than the mirror finish. But that mirror finish sure does look pretty in photographs and showroom displays!”

Portable soldering fumes extractor fan DIY (battery operated and USB rechargeable)

Here is a very simple fume extractor fan, to put an halt to apnea soldering.

Made of:

  • DC/DC buck boost converter (3€ on ebay)
  • USB battery pack 5€
  • scrapped fan
  • scrapped switch
  • scrapped potentiometer
  • Hammond prototype case (1€, same as my USB motion sensor)
  • nice labels
  • double side tape

Enough talk, a picture:

And in action, can suck up to 15cm at medium speed:

This “hack” took me 30min, and costs close to nothing, while some have been down to build a DC/DC converter for this!

Thing to add in the future:

  • active carbon filter for better filtering, but usable as is for small jobs: you don’t get fumes in your face anymore.
  • USB light for soldering in the dark

My favourite use: in the freezer/fridge, when you forgot to chill beers for an unexpeted party, it takes only 10min to have freezing beer instead of 1h. (remove the carbon filter first…)

USB connected digital multimeter and graph plotting (UNI-T UT61E and sigrok)

Ever wanted to have nice plot (U/I curve, whatever) simply plotted?

I got 2 UNI-T UT61E with USB cable (50€ each)

With sigrok you can easily get data from many device with a single command:

sigrok-cli –driver=uni-t-ut61e:conn=BUS.DEVICE -O analog  –continuous

Where BUS and DEVICE is replaced with the output of lsusb

lsusb
Bus 002 Device 002: ID 8087:8001 Intel Corp.
Bus 003 Device 086: ID 1a86:e008 QinHeng Electronics HID-based serial adapater
Bus 003 Device 087: ID 1a86:e008 QinHeng Electronics HID-based serial adapater

In my case, as I’ve 2 devices, so 2 different commands are used:

sigrok-cli –driver=uni-t-ut61e:conn=3.86 -O analog  –continuous

sigrok-cli –driver=uni-t-ut61e:conn=3.87 -O analog  –continuous

 

But what about logging in the same file the two ouputs simultaneously?

Here comes the magical function: paste and joined pipe:

paste <(sigrok-cli –driver=uni-t-ut61e:conn=3.86 -O analog  –continuous) <(sigrok-cli –driver=uni-t-ut61e:conn=3.87 -O analog  –continuous) > measure.csv

 

I’ll let you deal with the uber simple csv processing with octave or libreoffice calc (mV, mA range condition, etc…), as this blog entry is mainly used as a personal notepad.

 

Note: if you have trouble connected with sigrok, with an error. You may need to disable the power feature, with the script pointed by blog.philippklaus.de

#!/bin/bash
# see http://www.erste.de/UT61/index.html
for dat in /sys/bus/usb/devices/*; do 
  if test -e $dat/manufacturer && grep -q "WCH.CN" $dat/manufacturer; then
    echo "Suspending ${dat}."
    echo auto > ${dat}/power/control
    echo 0 > ${dat}/power/autosuspend 
  fi      
done

microSD card reflow: quick and dirty PCB with Kicad

Ever wanted to add a lot a flash memory to a small microcontroller? NOR flash or EEPROM are ok, but only for small size. For Gbit range, you need NAND, and with NAND comes CCR, LUT, wearleveling, etc… Furthermore, they are darn expensive in small volume.

SD and microSD card are very interesting: they cost nothing, and you just need a SPI interface as the controller is included.

Last night, I thought: “why not reflow a complete microSD card”, and save the cost of the socket, and PCB footprint size. As the card is composed of the same resin as chip casing and pins are flat bellow the microSD card and even gold plated, fore sure it should not be a problem to bring this to 270°C for 2-3 min….

Let’s try!

Here is the pinout

Then let’s create a small board, to try the reflow of a micro SD card and give access with some 2.54mm header.

Lets open Kicad and start with the schematic with Eeschema:

Then PCB new for the board layout:

Let’s submit the gerber files to OSH Park

Total including USPS post mail: 4.10€

That was my fastest board made ever, 1h30 from searching the pinout to the confirmation email!

See you back in few week for the oven reflow test!

Update: the board and the reflow!

First, let’s clean it and apply some flux:

Then some solder on the pads, and flux again:

Time to turn the heating plate and IR reflow on:

Just stir it a bit while it’s hot:

Houston, we have a reflow!

Then time to test: lets scavenge a super cheap reader microSD card reader:

And plug it: IT WORKS! After 3 min under the IR station, it does work.

I think I’ve to increase the pad size, in order to maximize the solder paste.

Now I’m confident sending to production, as I’ve quite a lot of theses cards in trays, ready for pick and place:

 

USB motion sensor (PIR) to activate monitor

I have an always on net-book for weather forecast (yeah, when paragliding, you need the most up to date forecast)
It basically displays a full screen custom web-page with time and date and weather.

Its always on, not really good for the back-light and energy consumption.

So I got the idea of plugging a PIR sensor to wake up the screen when someone approach it.

Take an Arduino Micro Pro (4€ for the Chinese version), a PIR sensor (2€), a Hammond case (1€) and an USB A male from scrap (0€).

Let’s give a try, with a basic wiring, and this sketch to emulate keyboard thanks to it’s USB HID, the Arduino Micro Pro is a must.

Updated 05-01-2017:

  • code with USB wakeuphost and capslock instead of ctrl
  • green TX led always on
  • orange RX led only on motion
#include <Keyboard.h>

#define SENSOR_PIN 10   // Senor state input pin
#define RX_LED_PIN  17  // The RX LED has a defined Arduino pin
static bool sensor_previous_state = false;

void setup()
{
  pinMode(SENSOR_PIN, INPUT);  // PIR sensor pin as input
  pinMode(RX_LED_PIN, OUTPUT);     //  RX LED as an output
  digitalWrite(RX_LED_PIN, HIGH);  //  RX LED off
  TXLED0;                     // switch on TX green to show init/powered up (only available by macro)
  sensor_previous_state = digitalRead(SENSOR_PIN); // get sensor initial state (can be already true)
}

void loop()
{
  bool sensor_current_state = digitalRead(SENSOR_PIN);
  if ( sensor_previous_state == false   // looping until we detect a rising edge
       && sensor_current_state == true) {// when sensor state is trigged, it takes about 20 sec to recover
    digitalWrite(RX_LED_PIN, LOW);   // set the LED on
    USBDevice.wakeupHost();
    Keyboard.press( KEY_CAPS_LOCK );
    Keyboard.release( KEY_CAPS_LOCK );
    TXLED0;                     // great hackery in this: we have to force down the TXLED
    delay(1000);                  // wait a bit for the led
  } else {
    digitalWrite(RX_LED_PIN, HIGH);    // set the LED off
    TXLED0;
  }
  sensor_previous_state = sensor_current_state;
}
2017 update: lightguide for green and orange LEDs:
p70105-114417
Update: LED lightguides from the scrap box
And voila!
Quite nice, discrete and works very well, for about 10€/$.