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Different projects

The purpose of this site is to describe some of my both big or small projects, where I tried to improve different products, build my own gadgets or solve annoying everyday problems.

My DPH3205 power supply

Power Supply with DPH3205

As a frequent Ebay and Banggood buyer it was hard not to notice advertisement for the interesting products of the Chinese company RD® i.e. Ruideng Technologies from Hongzhou. There are several digital programmable power converters: several buck, and one buck & boost converter with keyboard and display interface. I perform some Google search to see if it is something to have. Do these gadgets have enough quality? Are they enough accurate?

I stumbled on an interesting Danish site Lygte-info. This guy has spent lot of time testing different products. I was lucky to find here a very detailed test and review of the DPH3205 module. DPH3205 voltage interface This digital programmable power buck & boost module seems to be most interesting for me, because it is most versatile. It allows you to have fixed or variable DC input power source and to get variable regulated output from 0..32V and 0..5A with low heat dissipation. Or if you have DC input source with enough power, in already mentioned voltage range, it may be suitable as input power to this module to get whole output voltage range. Output voltage och current is obtained by help of rotary encoder knob or by calling previously programmed values from the unit memory.

After reading this detailed review, I was convinced that it is right thing for me. A DPH3205 for € 25 is irresistible interesting. I couldn't wait and made a purchase at Banggood. After less than 4 weeks arrived my package with well protected content. I immediately started my own testing of this module just to learn how to use and to be acquainted with it. Of course, I fell in love with it. I have realized how good and practical it would be if I made my own Power Supply with it. I checked my stock and find an SMPS Mean Well DRP-240-24, i.e. 24V/10A for the primary power source and tested them together. I was again surprised by performance of this module.

Mechanical construction:

I knew that most complex problem could be to find some appropriate enclosure. This used to be expensive and cost much more then the module itself. For many years on a shelf, in front of my eyes, I had a analogue barometer unit DPI 141, which just shows current Air pressure. It was discontinued and not used anymore in our products. DPI 141 has a perfect enclosure for this project: dimensions exactly as needed, two nice front panels and very useful flip-up front feet. I could not find anything better. At first, I thought it would be nice if it is possible to fit two of DPH3205 modules in it to get Power Supply with dual output. The box was not enough big for this purpose. Though it was excellent for a complete single regulated Power Supply and I made decision to build my own programmable Laboratory Power Supply!
I needed to make a minor purchase of a pair of 4 mm screw terminal post with a radial hole through it for an easier output wire or banana connection and access. Additional € 2 and about four weeks of waiting (I had lot of these without a radial hole). During that time I opened the barometer unit, removed all content, prepared front panels and made a completely new rear panel from a Schroff aluminum panel plate of 2.5 mm thickness. I cut out all holes I needed (for Mains switch Sw1, connectors X1 and X2) on the rear panel.
F10 termal circuit breaker On the upper front panel I removed original front sticker and replaced it with thin (1mm) aluminum plate with one surface in white turned outside. Two holes are needed here: one for the Display unit A2 and a hole for the F10 fuse and circuit breaker.
Lower front panel I kept unchanged, except the two identical holes for "banana" 4 mm screw terminals (red and black).
The inner in-between holder plate was perfect as it was and needed only some holes to be drilled: 4 holes for digital power module A1, 3 holes for the primary power supply PS1 and finally two holes for the 35 mm DIN rail which will keep Re1 Relay socket.

I won't present any mechanical drawings. The reason is that I did not use a commercial enclosure. The chance that you have the same box is very little. I spent little more time trying to make good photographs which are presented here in the photo album. You have to make your own adaptation for obtained enclosure.
Dimensions of my enclosure are:
- width = 190mm
- height = 140mm
- depth = 250mm

Schematic diagram of this Power Supply

During this work I developed an idea: if I made possibility to connect external power source (6..40VDC) too, then it would be possible to power this PS, for example: from my car battery, solar power panel or any other DC source (in required voltage range). It would be very practical and add more value to this project.

Schematic DHP3205 PS

By help of OrCAD I drew the schematic diagram for my Power Supply. I did not like to manually switch between these power input sources (X1 or X2) but want it to work automatically. For this purpose Re1 is used. Re1 works in this way:
1) When digital output power module A1 is supplied from electrical grid through X1, PS1 will activate Re1 and +24V output from PS1 is fed to the Re1:14. As the relay is in activated state, Re1:14 is connected to the Re1:11 terminal and then it goes to the F10 (airplane) fuse circuit breaker and finally continues to the Digital Programmable Output Power Module A1:In+ terminal.
2) If there is no Mains power, but external DC power source does exist, input power is fed through X2 (Phoenix) 20A plinth connector. Re1 is not activated in this case. The positive pole of the external voltage source is connected to the Re1:12 terminal and goes through the inactivated relay to the Re1:11 connection terminal, continues via F10 to the Digital Output Power Module A1:In+ terminal. In this case we may have any input voltage between 6..40VDC and it needn't to be stabile. The output module A2 will function properly.
For full output power, input voltage must be higher than 18VDC and and has minimum of 180W of power.
3) This design may have redundant input power supply. If input power is presented on both X1 (DC) and X2 (AC) connectors. Mains power will feed output module (described above under point 1.). If, of some reason, mains power disappears, this Power Supply will automatically turn to DC source from connector X2, almost without any interrupt. This is not an usual feature in an ordinary Power Supply.
Minus pole (GND) from both sources are connected directly to A1:In- terminal.

At any time you can switch off power to the output module A1 by pulling out the knob of F10 fuse (circuit breaker). When F10 is pulled out or tripped off automatically when over current is presented a white ring is exposed on the knobs body. It is shown on the F10's label too. This is a fuse and breaker at the same time.

I used three different wire gauges in this project:
1) AWG20 (0.5mm2) for mains part of the Power Supply. Blue (BU) for Neutral (N), brown (BN) for Line (L1) and yellow-green for Protective Earth (PE).
2) AWG24 (0.25mm2) for mating of Re1: A1(+), A2(-). Black (BK) minus relay polarity (A2) and red (RD) for plus relay polarity (A1).
3) AWG16 (1.5mm2) is used for the rest of connections. Black (BK) for minus polarity, GND. Red (RD) for plus polarity. Orange (OG) plus polarity X1 - Re1; brown (BN) between Re1 - F10 - A1.

Do not be fooled by thickness of used wires! I have used teflon i.e. PTFE (polytetrafluoreten) insulated wire. PTFE is much more thinner and temperature resistant than ordinary PVC insulation. These wires are approved for 13.5A/mm2 if the wire is laid free (which is the case here).

Bill of materials BOM:

D. Part no. Qty Description of the part Manuf.
A1, A2 DPH3205 1 Digital programmable buck&boost module Ruideng
PS1 DRP-240-24 1 SMPS 24V/10A 240VA MeanWell
X1 FN9260 1 Power entri 10A with 3.15A (x2) Schaffner
F1, F2 02183.15HXP/a> 2 5x20mm 3.15A fuse Littelfuse
X2 1840560 1 20A power connector (plinth) DFK-PC 4/3-GF-7,62 Phoenix
Re1 C7-A20FX 1 Relay with its socket 24V/10A Releco
F10 483-G411-K1M1-A1S0Z-10A 1 10A fuse and circuit breaker ETA
Sw1 C6053ALBR3-1197W-B 1 DPST panel rocker switch 250V/20A Bulgin
+, - 965386 1 pair 4mm banana screw socket, red & black on Banggood
- 1-966067-2 12 End sleve Black (AWG16) TE-connectivity
- 966067-2 7 End sleve White (AWG20) TE-connectivity
- 2-520184-4 7 Faston receptacle 6.3mm red TE-connectivity
- 34148 6 Ring terminal 4,3mm, red TE-connectivity
- 24291 4 M3x15mm standoff Keystone
- 35mm DIN rail 50mm 35mm DIN rail Any

Add some M3: nut, washer and screws of different length to fit all necessary details. Some label printer would be nice to have for example: Dymo 2000 or some of Brother brand.

Digital Programmable Power Module DPH3205 specifications:

User Instruction DPH3205

According to Ruideng's Operating instructions:
- Input voltage range: 6 - 40VDC
- Output voltage range: 0V - 32.00V
- Output current: 0A - 5.00A
- Max aloud input current: 10A
- Output ripple: about 100mVpp
- Output voltage resolution: 0.01V
- Output current resolution: 0.001A
- Environment temperature range: -10°C - 15°C
- For full output load, input source must be higher than 18V and 180W.
- Operation: CV, CC

My Power Supply specifications:

Everything what is sad for DPH3205 module is the same for my power supply.
- Dual input power source: internal 24VDC and external 6..40VDC
- Input power redundancy
- Automatic operation on available input power source
- Dimensions: W190mm, H140mm, D250mm
- Easy external power connection (connector + plinth)
- Convenient reading angle and access when front feet are pulled-out
- practical recessed currying handle

If you have some comment or suggestions, feel free to e-mail me.
Designed by: Marinko Orlovac, 2017.
Reviewed by: Tony Sunnarborg