HackerBoxes 0017: Power Maker

Power Maker: This month, HackerBox Hackers are exploring power electronics including various power supply converters. We are also modifying surplus power supplies into laboratory, bench supplies.

This Instructable contains information for working with HackerBoxes #0017. If you would like to receive a box like this right to your mailbox each month, now is the time to subscribe at HackerBoxes.com and join the revolution!

Topics and Learning Objectives for this HackerBox:

• Define Power Electronics and describe its importance
• Explain the difference between linear and switching mode power supplies
• Identify boost, buck, and buck-boost type switching power converters
• Power 5V USB devices using two AA cells into a boost converter
• Assemble a DIY USB power pack based on Lithium batteries
• Measure 5V USB power supplies under various resistive loads
• Modify and Fabricate a Laboratory Bench Power Supply
• Augment a fixed switching power supply with a variable output rail
• Upgrade a Serial to USB bridge module with a linear regulator
• Control Power Relays using Wi-Fi Internet-of-Things technology

HackerBoxes is the monthly subscription box service for DIY electronics and computer technology. We are hobbyists, makers, and experimenters. And we are the dreamers of dreams.

• HackerBoxes #0017 Collectable Reference Card
• Elite Maker Bench Supply Conversion Kit
• 5V USB Boost Supply (0.9V input)
• 5V Micro USB Lithium Battery Charger
• CP2102 MicroUSB to TTL Interface Module
• ESP-01 8266 Wi-Fi Module
• Opto-Isolated Dual Relay Module
• AMS11117 Linear Regulator
• USB Power Tester
• Power Resistors (10 ohm Loads)
• Dual AA Battery Holder
• USB Power Break kit with alligator clips
• DuPont Female-Female jumper wires
• Utili-Key 6-in-1 Key Ring Tool
• Exclusive Power Maker Keychain/Pendant
• Exclusive HackerBoxes Power Maker Decal

Some other things that will be helpful:

• Soldering iron, solder, and basic soldering tools
• 2 AA battery cells
• Rechargeable Lithium battery
• Tools and PC Power Supply for Lab Supply Conversion

Most importantly, you will need a sense of adventure, DIY spirit, and hacker curiosity. Hardcore hobbyist electronics aren't always easy, but when you persist and enjoy the adventure, a great deal of satisfaction may be derived from persevering and getting your projects working. Just take each step slowly, mind the details, and don't hesitate to ask for help.

Power Electronics is the application of solid-state electronics to the control and conversion of electric power.
(Wikipedia Entry)

AC to DC Converters are also called rectifiers. The are the most typical Power Electronics circuits found in the power supplies of many consumer electronic devices, such as televisions, personal computers, battery chargers. You probably have numerous of these around your house in almost anything that plugs into wall power (which is AC).

DC to DC Converters are used to convert one DC voltage to another DC voltage. These are often found inside of electronic systems downstream from an initial AC to DC converter to create various other DC voltages. They are also often found inside of battery powered systems to convert the voltage supplied by the battery to the voltage(s) required by the system. Two common types of DC/DC converters used in hobby electronics are linear regulators and switched-mode power supplies.

DC to AC Converters should be noted for completeness. They are generally called inverters or power inverters. You may keep a power inverter in your car, boat, or RV to convert the 12V DC vehicle supply to 120V (or similar) AC "wall power" or "mains power" in order to supply electricity to small appliances, pumps, and so forth.

Additional Resources

• PDF Book Chapter on Power Electronics
• YouTube EEVblog #90 on Linear vs Switched-Mode Converters
• University of Colorado Power Electronics Coursera
• Open Course Ware on Power Electronics from MIT
• YouTube playlist Fundamentals of Power Electronics from UNIST

As hobbyist and commercial devices increasingly leverage USB-style power connectors to provide 5V, it is useful to have a set of USB power breakout leads for experiments.

Start with a Male to Female USB extension cable, and a pair of alligator clip jumpers (one black and one read). Cut all three in the middle as shown in figure A.

Next, identify the +5V and GND lines. These are usually red and black, respectively, but you can test them with a voltmeter. The other two lines (USB signal will be lower voltage).

Finally, solder the alligator leads to the USB lines and complete with shrink tubing as shown in figures B and C.

These breakouts can be used to clip 5V into a circuit (or onto a load) from any USB power source. They may also be used to clip onto a supply and then plug in a 5V USB load.

A pass-through USB power tester can measure current and voltage of the power supplied by a UBS port. It can be used with a phone, mobile power pack, or any other load. The USB Power Breakout Leads from the previous step may also be used with a power dissipating resistor (or combination thereof) as a load.

Operating Parameters

• Input Voltage: 3 - 7V
• Input Current: 50mA - 3500mA
• Capacity: 0 - 19999mAh
• LCD can display voltage and current simultaneously
• Data storing feature
• High and low voltage alarms

The small button can be used to cycle test data.

Consider loading with various series and parallel combinations of the ten ohm power resistors. Do the various measured currents correspond to the calculated resistance loading 5V according to Ohm's Law?

A Boost Converter is a specific type of switched-mode power supply that can step up a lower voltage to a higher voltage.

This particular Boost Converter module can convert any DC voltage from 0.9V-5V to a nicely regulated 5.0VDC USB-style supply. The switched-mode used is Pulse-Frequency Modulation (PFM).

Powering with two AA cells can supply an output current of 500 ~ 600mA. A single AA cells can supply an output current about 200mA.

Specifications:

• Input voltage: 0.9V - 5V DC
• Output voltage: 5V DC
• Up to 96% Efficiency
• Dimensions: 34 (mm) x16.2 (mm)

This video details the operation of Boost Converter Circuits and even how we can make our own from scratch.

The Battcher Charging module features the TP4056 (datasheet) Battery Management Chip and the DW01A Battery Protection Chip with 8205A Dual MOSFET

Specifications:

• Input Voltage: 4.5~5.5V
• Full charging voltage: 4.2V
• Max output current: 1A
• Indicator LED: (red = charging, green = charged)
• Input: Micro USB Port
• Dimensions: 25mm*19mm.
• Use with 3.6V, 3.7V, 18650, polymer, and other lithium batteries
• Use with single-cell lithium or lithium multi-section in parallel

Here is a video detailing operation of the battery charging module.

This module, the boost module from the previous step, and a Lithium cell can be combined to create a DIY USB Power Bank as shown in this Instructable.

This Elite Maker activity starts with scavenging an ATX-Style Power Supply from a scrap desktop computer. The parts in the Conversion Kit are used to transform the scavenged supply into a Laboratory-Style Bench Supply. A power supply from an old PC should be easy to locate under your desk, from the IT department, or a thrift store. If all else fails, you can purchase a new, but inexpensive, power supply such as this one.

Bench Supply Conversion Kit Contents:

• Elite Maker Bench Supply Overlay Decal
• Five Red Binding Posts with mounting hardware
• Three Black Binding Posts with mounting hardware
• Variable Buck-Boost Converter with 1.2V to 35V output
• LED Panel-Mount Voltmeter
• Power Switch with mounting hardware
• Potentiometer 10K with mounting hardware
• Aluminum Knob for potentiometer
• Ten Ohm power resistors
• Various Heat Shrink Tubing
• Four Adhesive Rubber Feet

Other Items to Consider:

• Soldering Tools
• Hand Drill or Drill Press with standard bits
• Nibbler Tool
• Files (flat and round)
• Deburring Tool
• Hot Glue or Epoxy or Builder's Adhesive

It may be helpful to review this very detailed tutorial for a similar project.

This Instructable also covers a similar project.

ELECTRICAL SAFETY NOTICE

Power Supplies are dangerous and can hold charge long after they are unplugged. Before opening a supply, or even just working with the external output leads, unplug it from the wall and drain the output capacitors on EVERY power rail (each different voltage). Connect one side of a power resistor to Ground (any black wire) and then touch the other end of the power resistor for a few seconds each to 5V, 3.3V, 12V and so forth to drain each rail. Consult the color-code chart here as a checklist for the rails to drain. Do this every time you power the supply down and then need to work on it again.

If you do not feel comfortable working on your power supply, buddy-up with someone from a local Hacker Space, Maker Lab, or Ham Radio Club for assistance. Better safe than sorry!

MECHANICAL SAFETY NOTICE

Working with power tools, or even hand tools that are capable of cutting metal, is dangerous. Again, someone from a Hacker Space or Maker Lab would probably love to help you out before you cut a finger off or drill a hole in your spleen. Wear safety goggles. Seriously.

MEASURE TWICE, CUT ONCE

This conversion project is advanced and difficult. Slow down, take your time, read all instructions through first and proceed with great caution. Take plenty of time to plan your project (more on this later). If you decide not to break into your power supply, there is no shame in implementing an external option such as this one. You can put the binding posts into some perf board or plastic paneling and solder up the external leads from the power supply.

The follow steps can guide the process to mechanically modify the power supply housing:

1. Unplug the power supply.
2. Completely drain the capacitor charge on each and every rail.
3. Cut all of the external connectors off leaving about three inches of wire to work with.
4. Open the belly of the beast.
5. Note how filthy it is and clean it.
6. Examine the empty space inside the housing.
7. Plan the location for the binding posts - use overlay decal as a guide.
8. Plan the location for the power toggle switch.
9. Is there room for the variable supply components inside?
10. Completely Disassemble the Power Supply to just the housing.
11. Cut the holes (see notes below).
12. Apply a coat of spray-paint (optional).
13. Apply the overlay decal.
14. Mount the binding posts into the housing.
15. Mount the variable supply components (optional).

Regarding the holes, cut-out sizes are:

• Binding Posts - 7.4mm (5/16 inch)
• LED Volmeter - 45 x 26mm
• Potentiometer - 9.5mm (3/8 inch)
• Toggle Switch - 6.4mm (5/16 inch)

Consult this handy chart when finding nearest drill bit sizes.

Variations: The Overlay Decal may be cut apart such that portions of it may be used in different areas of the supply enclosure as space permits. Furthermore, when the variable supply is not being incorporated, the rectangular LCD voltmeter outline may be removed. Also, the strip of title text along the top of the decal may be placed elsewhere as in the example shown.

Using shrink tubing as necessary, wire everything up.

• Attach power rail wires to the binding posts (note color codes).
• Attach the skinny green wire from the motherboard connector to the toggle switch.
• Attach one of the ground wires (black) to the toggle switch.
• You may need a load resistor on the 5V or 12V rail (to ground).
• You can usually ignore the brown 3.3V sense wire.
• Consult the next step if you are including the variable supply option.
• Clip off any unnecessary wires.

Once everything is wired up, reassemble the power supply being very sure to securely reattach the chassis ground if you removed it early.

Attach adhesive rubber feet to the bottom of the supply housing to protect your bench/desk.

NOTE ABOUT THE TOGGLE SWITCH

If your scavenged supply already has a power switch (usually at the AC input lines), It is fine to just use that as your power switch. You can leave out the toggle switch supplied in the kit and just short the skinny green wire from the motherboard plug to ground (a black wire). With that short in place, whenever AC power is switching on by the original switch, the switcher will turn on.

If you do use the toggle switch, it should be wired between the skinny green wire on the motherboard connector and ground. The little metal toggle switch should not be anywhere near the fat AC wires coming in from wall power even if one of them is also a "green wire".

NOTE ABOUT LOADING RESISTORS

Some PC switching power supplies will not turn on or stabilize without a load. Some do not need a load at all. If your supply needs a load (doesn't appear to work correctly without a load), you can use one or more of the ten ohm power resistors. The load should be placed on the rail with the highest current output rating. This is generally 12V, but sometimes might be 5V - check your supply specs. The best option is two resistors in serial (20 ohm) between the rail and GND. If that doesn't work, drop it to one resistor (10 ohm) to draw more current. Sometimes a load on both 12V and 5V might be necessary, but that is very rare. Keep in mind that If someone else did need loading resistors or not is a function of their power supply and will not necessary apply to the supply you are using. If you do end up needing load resistors, try to use the highest resistance that works to minimize the current draw. Remember that these resistors will always be drawing current (wasting heat) when the supply is on.

Note that the variable output supply can be integrated into the bench supply (space permitting), or built up onto an external carrier, or omitted entirely.

The variable output is achieved using a buck-boost converter based on the XL60009 (datasheet). The buck-boost module can take any voltage from 5-32V as input, so either the 5V or 12V rail may be used.

The output voltage is continuously adjustable from 1.2V to 35V using a 10K potentiometer. The buck boost module is manufactured with a tiny 10K trimpot. The trimpot may be removed and replaced (as shown here) with the supplied panel-mountable, full-sized 10K potentiometer. An aluminum knob is included for the potentiometer.

The LCD panel-mountable voltmeter can display the present output voltage from the buck-boost converter, which is also wired up to the VAR(iable) binding-post. The Voltmeter has an integrated 0.56 inch LCD display and is capable of measuring 0-100 VDC.

The voltmeter has three wire leads (red, black, and white). The red wire is the operating supply for the meter and requires 3-30VDC, so it may be connected to the IN+ pad of the buck-boost supply (either 5VDC or 12VDC power rail). The black wire should be connected to the IN- pad of the buck-boost supply (GND). The white wire is the voltage to be measured and should be connected to the OUT+ pad of the buck boost supply which also connects to the VAR binding-post.

Here is an excellent video on the operation of buck-boost converters.

The binding posts can be also be mounted into a drive bay filler plate and spliced into the power supply leads. We wouldn't recommend doing this with a mission-critical PC, but if you already have a machine on your workbench for programming devices or running instrumentation, you can take advantage of its power supply as well.

A common type of USB to TTL Serial Board uses the CP2102 chip (datasheet). The CP2102 has an on-board 3.3V regulator, but it does not supply enough current to power an ESP8266. However, there is plenty of current on the 5V rail since it connects directly to the USB 5V supply. Using an AMS1117-3.3 (datasheet) regular to convert some of the 5V current to 3.3V solves the problem quite easily and provides a great soldering exercise. The AMS1117 is a Linear Regulator variety of DC to DC power converter.

This Instructable shows this modification in detail.

The ESP8266 module can be used to control a relay module over over Wi-Fi. Using the modified CP2102 from the previous step, the entire project may be powered from a micro USB port.

This tutorial, and many others, explain programming the microcontroller core of the ESP8266 via the Arduino IDE.

Several other Instructables, such as this one, demonstrate similar projects. Note that the one in the link is not powered over the USB module.

ELECTRICAL SAFETY NOTICE

Switching mains power using power relays is dangerous. Such activities should be undertaken with great care, using properly grounded enclosures, and according to your local laws and regulations. If you do not feel comfortable working on power switching, we urge you to only work with switching low voltage signals. As suggested earlier, you can also buddy-up with someone from a local Hacker Space, Maker Lab, or Ham Radio Club for assistance. Better safe than sorry!

The Utili-Key from Swiss+Tech is a 6-in-1 Key Ring Tool. It is a super-handy, ultra-lightweight multi-tool and the perfect functional accessory for the HackerBoxes exclusive PowerMaker Keychain.

The Utili-Key 6-in-1 Multi-Tool includes:

• Flat Screwdriver
• Phillips Screwdriver
• Precision Screwdriver
• Straight Blade Knife
• Serrated Blade Knife
• Bottle Opener

Thank you for joining our adventures into power electronics. If you have enjoyed this Instrucable and would like to have a box of electronics projects like this delivered right to your mailbox each month, please join us by SUBSCRIBING HERE.

Reach out and share your success in the comments below and/or on the HackerBoxes Facebook page. Certainly let us know if you have any questions or need some help with anything. Thank you for being part of HackerBoxes. Please keep your suggestions and feedback coming. HackerBoxes are YOUR boxes. Let's make something great!