Power Supply Introduction
General
This stage supplies the "regular" 5 volt power rail, for powering the CMOS chips on the main part of the board.
Note: throughout these notes, they will refer to the board in terms of:
- Topside: the side where one can read the silk-screened component designations and outlines
- Bottomside: the reverse of topside, where the SMT components are installed
- Bottom or "bottom edge": the edge of the board where all of the connectors are located
- Top or "top edge": the edge of the board opposite of the bottom edge
Unlkess otherwise noted, all photos/graphics of the board layout are displayed herein with the top edge UP.
(go directly to build notes)Power Supply Schematic
(Resistor testpoints (hairpin, top, or left-hand lead), as physically installed on the board, are marked in the schematic with red dots)
(Click for Full Schematic)
(go directly to build notes)
Power Supply Bill of Materials
Stage Bill of Materials
(resistor images and color codes courtesy of WIlfried, DL5SWB's R-Color Code program)
| Check | Designation | Component | Marking | Category | Orientation | Notes | Circuit |
|---|---|---|---|---|---|---|---|
| ❏ | /QSD EN | shunt wire (cut-off lead) | Cutoff | (use for regular GND connection point) | Power Supply | ||
| ❏ | D3 | 1N4003 | 1N4003
 | Axial | Power Supply | ||
| ❏ | mtg_hdw | 4 X #4-40 hdw (nut, bolt, washer, spacer) |
 | HDW | Can install later. four each of 3/8 inch 4-40 Phillips head screws,4-40 nuts, 1/8 inch long #4 nylon spacer and #4 nylon washer | Power Supply | |
| ❏ | PCB | Ensemble RX PCB (board) | Main Board | Power Supply | |||
| ❏ | R14 | 68 1/6W 5% | bl-gry-blk-gld
 | 1/6W | S-N | Power Supply | |
| ❏ | U07 | LM78L05 voltage regulator | LM78L05
 | TO-92 | Power Supply | ||
| ❏ | C04 | 4.7 uF 10% 16V X7R RAD | 475
 | Ceramic | horiz | Power Supply | |
| ❏ | C05 | 4.7 uF 10% 16V X7R RAD | 475
| Ceramic | vert | Power Supply | |
| ❏ | J03 | DC Power Jack PCB Mount (rt-angle) |
 | Jack-RA | Power Supply | ||
| ❏ | P1 | DC Power Plug 5.5/2.1mm Pos Ctr |
 | Plug | Power Supply |
Power Supply Summary Build Notes
- Install Power Supply Components
- Install /RX EN (Ground Point)
- Test the Stage
Power Supply Detailed Build Notes
Top of the Board
Install Power Supply Components
Install the Diode with the lead on the cathode (banded) end forming a hairpin lead and the anode end snugged up against the board.
| Check | Designation | Component | Marking | Category | Orientation | Notes |
|---|---|---|---|---|---|---|
| ❏ | D3 | 1N4003 | 1N4003
| Axial | ||
| ❏ | PCB | Ensemble RX PCB (board) | Main Board | |||
| ❏ | R14 | 68 1/6W 5% | bl-gry-blk-gld
| 1/6W | S-N | |
| ❏ | U07 | LM78L05 voltage regulator | LM78L05
| TO-92 | Take ESD precautions | |
| ❏ | C04 | 4.7 uF 10% 16V X7R RAD | 475
| Ceramic | horiz | |
| ❏ | C05 | 4.7 uF 10% 16V X7R RAD | 475
| Ceramic | vert | |
| ❏ | J03 | DC Power Jack PCB Mount (rt-angle) |
| Jack-RA | ||
| ❏ | P1 | DC Power Plug 5.5/2.1mm Pos Ctr |
| Plug |
Install /RX EN (Ground Point)
Use a good strong piece of wire, as this will be used as a ground connection point for a number of tests throughout the build.
| Check | Designation | Component | Marking | Category | Orientation | Notes |
|---|---|---|---|---|---|---|
| ❏ | /QSD EN | shunt wire (cut-off lead) | Cutoff | (use for regular GND connection point) | ||
| ❏ | mtg_hdw | 4 X #4-40 hdw (nut, bolt, washer, spacer) |
| HDW | Can install later. four each of 3/8 inch 4-40 Phillips head screws,4-40 nuts, 1/8 inch long #4 nylon spacer and #4 nylon washer |
Power Supply Completed Stage
(These photos were of an earlier board design. It has changed since the author built the kit upon which these notes are based. The board layout graphics are, however, current.)Top of the Board
Power Supply Testing
Current Draw
Test Setup
Measure the resistance (after the input diode) on the power input to ensure there is no short circuit. Measurement can be taken from the hairpin of D3 and the "/QSD EN" ground wire and should read in the Megohm range.
If the measured input resistance is within reason, measure the current draw with your mA meter inserted in series into the positive power lead.
See Tutorial on Measuring Current for an illustration of how to measure current in a circuit.
Test Measurements
| Testpoint | Units | Nominal Value | Author's | Yours |
|---|---|---|---|---|
| D3 hairpin lead (WRT GND - "/QSD EN") | ohms | > 1M | 7 M and rising | _______ |
| Current Draw | mA | < 8 | 4.3 | _______ |
Voltage Test
Test Setup
With 12 V dc applied to the board (author's gel cell was at 12.89 Vdc), measure the voltage after D3 and measure the output of U7 (the 5 Vdc rail)
Measurements are with respect to (WRT) the regular ground plane (i.e., the non-USB side) of the board.
Test Measurements
| Testpoint | Units | Nominal Value | Author's | Yours |
|---|---|---|---|---|
| At Cathode of D3 (WRT regular ground) | Vdc | .6V less than input | 12.3 | _______ |
| At hole for R27 hairpin lead (WRT regular ground) | Vdc | 5 | 4.92 | _______ |