RadAsm30 Files

Digitaly controlled powersupply.
--------------------------------

Specifications
--------------
  o Alalog output (uses LM317T)
  o Digital control (uses STM32F103C8T6 and 1.8 inch LCD)
  o Output voltage
    - 0 to 15 volt
    - 10mV resolution
    - Slow rise
    - 4 presets (3.3V, 5.0V, 6.0V and 12.0V)
    - Optional battery backup to save your settings
    - 2% accurancy
  o Output current
    - 0 to 1.0 ampere
    - 1mA resolution
    - 3% accurancy
    - 1 ms overcurrent time to cutoff

Parts needed
------------
  1 x STM32F103C8T6 (Blue pill) and ST-Link programmer
  1 x Buck step down voltage regulator
  1 x B0505S 1W voltage converter
  1 x 1.8 inch SPI LCD with ST7735 controller
  1 x LM317T TO220 adjustable voltage regulator
  1 x TO220 insulation set
  1 x TLE2072 DIL8 IC, 2 x OP Amp
  2 x 1N4148 Diode
  3 x 1N4007 Diode
  1 x Blue LED
  1 x 200 ohm trim pot.
  6 x Tactile switch
  2 x 40 pin single row female header
  1 x 8 pin single row female header
  1 x Black banana socet
  1 x Red banana socet
  1 x Mains on / off switch
  1 x 10cm x 16cm double sided pcb
  1 x Alumina sheet heat sink
  1 x DIY casing

NOTE:
If you order the LM317T and TLE2072 from China (AliExpress) you
MUST verify that they are not fake.
I have found that there are fakes of both the LM317T and TLE2072 out there.
You should order them from a known good source.
NOTE:
There are several versions of the 1.8 inch SPI LCD. Verify that you get the
version with the correct pinout (blue PCB with memory card connector).

Optional backup battery
-----------------------
  1 x 1N4148 Diode
  2 x 1.5V button cell or 1 x 3V lithium

Optional power source
---------------------
  1 x 18V laptop power supply
  or
  1 x 15V mains transformer
  4 x 3A rectifier diode or 3A bridge rectifier
  1 x 4700uF 25V electrolyte

Capacitors
----------
  2 x 100n ceramic or chip capacitor

Electrolyte 16V unless noted
----------------------------
  1 x 470u 25V
  1 x 220u
  2 x 100u
  1 x 22u

Resistor 1/4W 1% metal film
---------------------------
  3 x 0R5
  1 x 33
  2 x 220
  2 x 330
  2 x 470
  1 x 820
  1 x 1K
  1 x 2K2
  2 x 4K7
  1 x 10K
  1 x 22K

Programming the STM32F103
-------------------------
Open the DigitalPSU project in RadSTM32 and build the project.
Connect thee ST-Link programmer to the STM32F103 and to yor PC's USB port.
Hit Run button. Verify that the programming was successful by scrolling
throug the output window to view the result.

Creating the PCB:
-----------------
I am using:
  HP Laserjet Professional P1102 printer.
  A4 toner transfer paper.
  Cooking ware with a flat, thick bottom and
  heating it to around 150C on the stowe.

Printout:
  If you are using different printer / paper size
  then adjust the size of the outer thin frame
  on both the top and bottom PCB designs. You
  must have exactly 2.54mm (0.1 inch) pitch. 
  The printout is landscape.

Preparations:
  Clean the PCB, avoid touching the copper after cleaning.
  I am doing the bottom PCB side first.
  Wrap the printout around the PCB and secure it with masking tape.

Toner transfer:
  Place the PCB on a thick pice of cloth, paper side up.
  Heat up the cooking ware. Place it on the PCB and apply as much
  presure as you can. Wriggle it around and pay extra attention
  to the PCB edges.

Removig the toner transfer paper:
  Soak the PCB in warm water for a few minutes.
  Remove the paper by rubbing the PCB with your thumb.
  If the transfer was successful you dont need to be
  careful. Inspect and make shure you got rid of all the paper.
  Minor errors can be fixed with a permanent ink pen.

Etching:
  Cover the top side with packing tape and etch the PCB.

Drill hples in upper left and bottom right corners.
You need these holes when you align the PCB top and bottom.
Repeat the process with the top PCB side. Make shure you
allign and orientate the top and bottom correctly.

Drilling the hples:
  I am using a home made hand held drill with a motor from
  an old worn out electric toothbrush. The drill bit is 0.6mm.
  Use a 0.8mm drill bit for the connectors and where larger
  holes are needed.

Soldering:
  Use a fine tiped soldering iron and thin (<=1mm) soldering tin.
 Step1:
  Solder all the feed throughs.
 Step2:
  Solder the buck converter and adjust it to 5.0V.
 Step3:
  Solder the B0505S 1W voltage converter.
 Step4:
  Solder the headers for the MCU and LCD.
 Step5:
  Solder the switches.
  At this point you should check for bad soldering and solder briges.
  You can also test if everything is working as expected by plugging
  in the STM32F103 and LCD and use an USB cable connected to your PC
  and the STM32F103. Unplug everything after testing.
 Step6:
  Solder all resistors, capacitors, diodes, trim pot. and electrolytes.
  Set the trim pot. to mid position.
  Wait with the LED until you have made the front panel.
 Step7:
  Assamble the front panel and solder the LED.

Testing and error corrections:
------------------------------

 Zero volt anjustment:
  Set PSU to 3.3V and outut off (blue LED off).
  Adjust trim pot. till you get an output of 0V.
  A few mV +/- is OK.

 Zero current adjustment:
  This correction is done in software.
  Set PSU to 3.3V and outut on (blue LED on).
  Example:
  Shown current is 0.015A
  #define AMPSERR ((float) 15.0) in Amps.c.
  Rebuild project and program the STM32F103.

 Current error correction:
  This correction is done in software.
  Set the measured output to 2.20V using a multimeter.
  Connect a 22ohm resistor at the output
  If the shown current is not 100mA the (3 x 0R5) resistor
  value must be corrected.
  Example:
  Shown current is 118mA

                 118
  Rx = 0.16667 * --- = 0.19
                 100

  #define AMPSOHMS ((float) 0.19) in Amps.c

 Voltage error correction:
  This correction is done in software.
  Set PSU to 3.3V and outut on (blue LED on).
  Measure the output voltage using a multimeter.
  Example:
  If you get an output of 3.18V then set
  #define VOLTSERR ((float) 12.0) in Volts.c (3.30 - 3.18).
  Rebuild project and program the STM32F103.

KetilO