§ 2.10 - Positive and Positive Power Supply, Regulated

Before you attempt this build, please:

• Read through the numbered build procedure with the idea of performing the listed steps in order
• Examine the PCB layout
• Examine the schematic diagram
• Refer to each of the linked pages in the "See also" list

This will help ensure that you will have the best possible experience, resulting in a build that works the way you expect it to.

Schottky diodes are recommended; these diodes have a much lower forward voltage drop, and so will waste less power and run cooler under load.

1. Optional: Install test points — Important: If these are used, they must be first components installed!
2. D1 — at least a PIV equal to the total secondary voltage of T1, 2 amps or more. Observe polarity.
3. D2 — at least a PIV equal to the total secondary voltage of T1, 2 amps or more. Observe polarity.
4. D3 — at least a PIV equal to the total secondary voltage of T1, 2 amps or more. Observe polarity.
5. D4 — at least a PIV equal to the total secondary voltage of T1, 2 amps or more. Observe polarity.
6. D5 — steering diode — at least a PIV equal to the total secondary voltage of T1, 2 amps or more. Observe polarity.
7. D6 — steering diode — at least a PIV equal to the total secondary voltage of T1, 2 amps or more. Observe polarity.
8. R1 — calculate the ohms and watts values for R1 here.
9. R2 — calculate the ohms and watts values for R2 here.
10. C1 — ceramic .22 uF — equal to or higher than the total secondary voltage voltage of T1
11. C2 — ceramic .22 uF — equal to or higher than the total secondary voltage voltage of T1
12. C3 — ceramic .1 uF — equal to or higher than the total secondary voltage voltage of T1
13. C4 — ceramic .1 uF — equal to or higher than the total secondary voltage voltage of T1
14. C5 — Polarized electrolytic — Calculate the uF and WV value of C5 here. Observe polarity.
15. C6 — Polarized electrolytic — Calculate the uF and WV value of C6 here. Observe polarity.
16. IC1 — 78xx-series three-terminal positive voltage regulator. Observe polarity. See Heatsink Considerations. Consider off-board mounting.
17. IC2 — 78xx-series three-terminal positive voltage regulator. Observe polarity. See Heatsink Considerations. Consider off-board mounting.
18. LED1 — a low-power LED of whatever color you prefer. Observe polarity.
19. LED2 — a low-power LED of whatever color you prefer. Observe polarity.
20. T1 — Center-tapped-winding secondary power transformer (see Choosing a Transformer)

Tip:

Single
connection

The footprints for filter capacitors C5 and C6 are designed to accommodate many different capacitor sizes and lead spacings. Each of the four-hole "diamonds" is one connection; you can use any one of the four diamond through-holes to connect one lead of your capacitor(s.)
 
Carefully observe polarity as shown in the layout diagram below (note that some of this build's placements are not the same as those marked on the board) and connect each lead of your filter capacitors into the correct diamond.

Positive and Positive Power Supply, Regulated, Build Guide
Some components do not match PCB silkscreen

+/+ build regulator placement
Note both reverse orientation and
shifted pin-to-hole alignment at right
for second 78XX-series regulator

Output Connection Detail

Plus-plus build schematic

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