Update #5: Manufacturing starts today!!
PNMini backers are all around the world!
(This map doesn't show all exact locations, because your information is kept private by Kickstarter and I am not able to see your location until May 7th. For those of you who don't see your country or city on the map and would like me to add a pin, just let me know in which city you live. I am more than happy to mark it on the map!! :P Great thanks to your support from all around the globe! :P )
PNMini will be available on
PNMini story is on
Updated FAQ: Why negative output?
What is PNMini?
PNMini is a family of high performance, easy-to-use DC/DC Power Modules for DIY electronics.
PNMini can be used as positive supply or negative supply. If both positive and negative supply rail are needed, just connect two PNMini modules together. No hardware changes are required.
PNMini is available in a small PCB package that enhances thermal performance and allows for hand soldering or plugin use. It provides +3.3V/-3.3V, +5V/-5V, or +12V/-12V output directly to your circuits requiring no external components.
PNMini family has two output current options to meet your system needs:
- PNMini-500mA: supports up to 500mA output current
- PNMini-2A: supports up to 2A output current
Find the DATASHEET!
In case the link above doesn't work, try this one: https://drive.google.com/file/d/0B0aPceJUD-kdSUVuLXQxZHlqcHM/edit?usp=sharing
Shown in the figure below is a PNMini-2A module. All the application instructions given below use PNMini-2A as an example. The PNMini-500mA version is similar in terms of how to use. Detailed specifications and test data of PNMini-500mA will be available after the final test is done.
How do I use it?
Supply Rail Configuration
PNMini is extremely easy to use. There is no external component required. The three terminals of PNMini are input voltage VIN, output voltage VOUT, and ground connection GND. The VIN pin is always fixed as Pin 3. Depending on the system requirements, Pin 1 can be positive output VOUT(+) or GND; Pin 2 can be GND or negative output VOUT(-).
The input range of the PNMini family is very wide to cover more DIY electronics applications. For PNMini-2A, the input range for positive output is 3.5V to 27V. The input range for negative output is 2.7V to 27V.
The output voltage is programmable through three feedback resistors connected from VOUT terminal to GND terminal.
PNMini can be used in all kinds of DIY electronics projects. Below are two application examples:
1. Arduino drone with longer battery life
PNMini can be used to power your Arduino drone. A miniature Arduino board is usually powered by 3.3V. The motors and sensors are usually 5V. You can use 3 li-ion battery stack and two PNMini to get the voltage you want! It's more efficient than LDO. PNMini provides up to 92% efficiency while LDOs can hardly achieve more than 50% efficiency. That's a 40% longer battery life for your design!
2. A simple ECG amplifier
Another application example is a simple ECG amplifier which can display your ECG waveform on a oscilloscope. For sensor or amplifier applications, dual supply is often preferred. Positive supplies are everywhere, but sometimes it's difficult to find a negative power supply. PNMini solves the problem by generating both positive and negative supply from a single source.
How does it work?
PNMini combines positive and negative supply capability into one module. The positive supply is a buck converter; the negative supply is a inverting buck-boost converter. Some buck converter controller ICs can be used as inverting buck-boost converter controllers. A Texas Instruments application note has one such application.
The figure below shows that if you switch the diode and the inductor in a buck converter, it becomes a buck-boost converter. And this is how PNMini works.
What about the technical details?
More key features of PNMini-2A module are:
- High efficiency at light loads: 85% efficiency at Vin=7V
- Typical 5uA shutdown quiescent current
- Slow start limits inrush currents
- Under voltage lock out (UVLO) protection
- Over voltage transient protection
- Thermal shutdown protection
- Cycle-by-cycle current limit enables short circuit protection
How efficient is it? Shown below are some test data:
How does the efficiency compare with 7805/7905? PNMini is a DC/DC switching regulator, which can easily achieve more than 90% efficiency; 7805/7905 are linear regulators, the efficiency is usually below 50%, depending on the input and output voltages, and the quiescent current of the regulator. The efficiency of a linear regulator can be estimated by Efficiency = Vout/Vin * 100%, if the quiescent current is very small. From the equation, at a certain Vout, the higher the input voltage is, the lower the efficiency is. Below is a comparison of PNMini vs. LM7805.
How does it achieve high efficiency at light load? At light load, the switching noise become significant. Instead of always switching, PNMini enters a mode called "Burst Mode", meaning that it switches for a certain amount of time, and then stops switching. When the output voltage drops below a certain level, it switches again. In this way, the switching loss is reduced at light load, thus the efficiency is improved.
What kind of protections does PNMini have? PNMini is a very robust design, it has over voltage protection, thermal shutdown protection, and short circuit protection. The way it protects itself from damage from a short circuit is by a technique called "cycle-by-cycle current limiting" - if the current exceeds a certain level, PNMini will cut the PWM waveform of the current cycle thus limits the current from growing.
What about the other specifications such as line regulation, load regulation, start up, transient response, and output voltage ripple? Don't worry! The PNMini solution is FULLY tested. It's not something you get from eBay and get nothing but a board. You get comprehensive test data on each of the specification!!
PNMini lab test:
How did you make it and what are the next steps?
I'm a maker and I love electronics. For every electronic circuit I built, I need a power supply for it. Power supply design is usually not the interesting part of the circuit, but you have to do it and make it a robust design. It's an annoying fact that you have to design a power supply circuit over and over again. So I design to make it modular.
There are many good positive dc-dc modules you can get from eBay, you can hardly find a negative power supply. And even for the positive supply, the problem is, what you get from eBay is a black box. You get very limited information of the board. When you test it yourself in lab, you may find that at light load the efficiency is really poor, or the ripple voltage does not meet the requirement of your system. So I want to make a high performance dc-dc module that I know everything of it, and I want it to support both positive and negative supply.
This is the first PNMini prototype soldered by hand, and it's intended for a MSP430 controlled weight sensor application.
After the first prototype, I made a 2A PNMini, as shown in the first section. I tested intensively in lab and generated the PNMini-2A datasheet. Then I made a 500mA version of PNMini. Shown below is a small USB charger using PNMini-500mA prototype v1:
Two PNMinis are planned - 500mA version and 2A version. This covers very wide applications for DIY electronics. The PCBs for PNMini family are in line and ready for production. Shown in the figure below are PNMini-2A and PNMini-500mA new PCB with optimized routing:
The prototype is fully tested and functioning well. Production will start immediately after successfully funded. The unit cost is inversely proportional to the amount. The cost consists:
- PCB board cost. The PCB board cost is very high if the volume is low. Above is a PCB cost estimation from an online quote comparison tool. It is calculated by assuming that we'll order 300 boards at a time. From the quote, the total PCB cost of 300 boards with 2 layers and silkscreen is around $300, and it'll be a one week turn.
- Component cost. Assuming 300 units, the total cost of all the components on board is around $3 per unit, including integrated circuits, diodes, inductors, capacitors, resistors, and pin headers.
- Assembly and test cost. If the amount is below 300 units, we will be forced to solder all units by hand because of the cost, and I will testing all the units by myself in my lab - which is very time consuming. If the we get more than 300 units, we'll be able to use soldering machine service and the test service provided by the factory.
- Package and shipping cost. We'll use USPS standard service inside US. Additional cost will be added for international shipping.
We plan to begin manufacturing after successfully funded. But we can start manufacturing immediately if the number of orders reaches 300 units.
If we get more than enough funding, we plan to add a color package to PNMini family. The package will be heat dissipation and provides insulation for the internal components. PNMini logo and pin names will be printed on the package. Color package will be available in the retail version after kickstarter funding period ends, if we get enough funding.
Below are several sample package we made:
Power supply modules are like nails to your furniture. You will need a power supply circuit for each of your design. PNMini will accelerate your design process, and leave the most interesting part of the design to you. I hope this idea is beneficial to the makers community.The cost of new PCB production is very high. What I need is your support. With your help, PNMini will be made open source and get into your hand.
Thank you for your time and support!!!
Risks and challenges
The design itself is very robust. As a power supply design professional, I guarantee that it is high quality, and I will test every module and make sure it works before I send it to you (if you choose a starter kit and want to solder it yourself, I will provide a very detailed assemble guide, and a user's manual to make sure that you can power it up).
The biggest risk at this point is being able to meet demand. I set the funding at the level that I estimated to be enough for manufacturing. If the demand is high, it may at first take a little longer to fill orders than I would like. I have plans to expand production if needed to accommodate higher order volumes. If the demand does not meet, I won’t be able to kick off the fabrication.
This is my very first project on Kickstarter, please help me on make it a reality, and help me share this great idea to more makers!Learn about accountability on Kickstarter
- (50 days)