Project 021 - Home Built Bench Power Supply

Details: Hits: 113320

DISCLAIMER: This design is experimental, so if you decide to build one yourself then you are on your own, I can't be held responsible for any problems/issues/damage/injury that may occur if you decide to follow this build and make one yourself.

INTRO

My workshop has a couple of bench power supply's, one is an old Farnell TOPS 3D 3-rail tracking job, and the other is a 3-rail CSI CSI3005XIII with Constant Current functions. The farnell is all analogue but has no constant current control (current limiting only). The CSI is good but out the box doesn't allow you to preset the constant current setting and thats what I want.

So, rather than buy another PSU I thought i'd design and build my own.

This is not a full design blog and I do not have the schematic, pcb files or code available (please don't ask)........it's just posted here as a hint as to what I get up to in my workshop.

Inspiration for my design comes from EEVblog.com & gerrysweeney.com.

SUPPLIER INFO

Front panel = Schaeffer AG - http://www.schaeffer-ag.de/index.php?L=1

Enclosure = KEL p/n - CVR1427 enclosure (purchased via Ebay). The manufacturer is http://www.varisom.com

TECHNICAL

Dual channel 0-24vdc @ 3A each, pre-settable CC, fully isolated and with independant voltage/current control.
Resolution = 10mV (across 0-24vdc).
10-turn pots & numeric keypad for the main voltage (CV) output adjustments.
1-turn pots for main current (CC) output setting.
Output tracking mode (Ch.2 will follow Ch.1).
Latched pushbuttons for disabling the outputs (effects both software & hardware in order to make output 0vdc).
Switching regulator tracking pre-regulator / BJT power transistor main regulator.
ACS712 Hall effect based output current sense IC (0-5A).
Atmel328P (Arduino bootloader) monitored/controlled.
Dual 128x64 backlit LCD's (large fonts using the "u8glib" universal 8bit Graphics library from code.google.com/p/u8glib/).
Control board - Dual layer Pcb, 90% SMD.

I/O

Arduino I/O. Based around an ATMEGA328P-A (16MHz):

D0 - Rx FTDI conn.
D1 - Tx FTDI conn. & Buzzer output
D2 - DI - Fan speed monitor (INT0)
D3 - DO - Fan PWM
D4 - DI - SW1 DI Pushbutton (latched) - Zero main output
D5 - DI - SW2 DI Pushbutton (latched) - Disable CC on main output
D6 - DI - Ch.2 Current Limit monitor
D7 - DI - Ch.1 Current Limit monitor
D8 - S/W SPI - LCD2 SID
D9 - S/W SPI - LCD2 CS
D10 - S/W SPI - LCD2 SCLK
D11 - H/W SPI - LCD1 SID
D12 - H/W SPI - LCD1 CS
D13 - H/W SPI - LCD1 SCLK

A0 - spare
A1 - spare
A2 - AI - Ch.2 Current potentiometer (front panel)
A3 - AI - Ch.1 Current potentiometer (front panel)
A4 - I2C SDA
A5 - I2C SDL
A6 - spare
A7 - spare

I2C ADC (MCP3424 18-bit Quad input +/- 2.048v) - Control Section
CH.A - Ch.1 Voltage potentiometer (front panel)
CH.B - Ch.2 Voltage potentiometer (front panel)
CH.C - spare
CH.D - spare

I2C ADC (MCP3424 18-bit Quad input +/- 2.048v) - Channel 1
CH.A - Ch.1 Pre-reg Voltage monitor
CH.B - Ch.1 Pre-regulator voltage monitor
CH.C - Ch.1 Voltage output monitor
CH.D - Ch.1 Current output monitor

I2C DAC (DAC8574IPW 16-bit Quad output 0-5vdc) - Channel 1
CH.A - Ch.1 Voltage output control
CH.B - Ch.1 Current output (CC) control
CH.C - spare
CH.D - spare

I2C ADC (MCP3424 18-bit Quad input +/- 2.048v) - Channel 2
CH.A - Ch.2 Pre-reg Voltage monitor
CH.B - Ch.2 Pre-regulator voltage monitor
CH.C - Ch.2 Voltage output monitor
CH.D - Ch.2 Current output monitor

I2C DAC (DAC8574IPW 16-bit Quad output 0-5vdc) - Channel 2
CH.A - Ch.2 Voltage output control
CH.B - Ch.2 Current output (CC) control
CH.C - spare
CH.D - spare