MintyBoost! - Small Battery-powered USB Charger

by:CTECHi     2019-11-24
The next 10 steps detail how I came up with ideas, hardware, design, etc.
This project.
It\'s not 100% correct, but it\'s very close.
Since it took only 2 days for this project (on & off)
To design/test/release, tracking is much easier than something huge like x0xb0x.
I also include Schematic/layout files in Eagle format.
Prototype 1 is best etched at home (
One side of it)
Okay, so where does an idea come from?
This is the only important issue and the most difficult one.
I think I have to say, this is because I saw this half.
A dozen items: * Aaron Dunlaps 9 v USB charger * Another 9 v 7805 USB charger (Instructables)
* 9 V 7805 USB \"battery\" for Jason Streigel \"(hackaday)
* Ians FireWire switch charger (Instructables )
* Firewire chargerOK for 9 v AA from Chris DiClerico, I might even have missed some.
What is the theme here?
9 v and 7805 are used for almost all batteries (
A very common linear 5 v regulator: from 7-18V input).
This design is great because the 7805 is great and the 9 v offers 7-
9 V depends on how they \"die.
However, one of the things I learned about 9 v is (
From a lot of bad experiences).
One is they don\'t have a lot of amps-
Hours: how much current is it (amps)
How long can they provide and provide (hours).
Available in Duracell 9 v-about-
500 mAh in its life. That\'s 500 mA (or . 5A)
100 mA for 1 hour or 5 hours.
This number is somewhat idealistic, but it is a good starting point.
Another problem is that they don\'t like to provide a lot of current because they have a high internal resistance (~2ohms)
But basically it just means that if you want a lot of current (
Let\'s say revive a drainage device)
9 v will not provide all 500 mAh but may be more like 400. (
Then say you want to draw 250 mA. 25A*2ohm = 0.
5 v lost internal resistance.
For more information on 9 v, please read the duracell datasheet)
Another problem with the 9 v 7805 scheme is that 7805 is a linear regulator.
That means if you want to get 100 mA at 5 v
Basically, USB power)
Then you take 100 mA at 9 v and lose 4 V * 100 mA = 400 mW (. 4W)
Poor as hot.
When the battery is worn to 7 v, the heat loss drops (7-5V)*100mA=.
But you are still very inefficient.
The highest efficiency is 72% (5V/7V)
Worst of all, it\'s 55%. 5V/9V)
This means you will lose about a third battery to heat up!
I will also point out that the static current of 7805 itself is about 5 mA, so you will always lose 5% (5mA/100mA)
Efficiency is just for supervision! (
& This is at least because if you charge the battery at a speed of 50 mA, then 5 mA of the static power is 10%)
OK, basically the 7805 + 9 v solution works, but the efficiency is very low, like around 60%, only 300 mAh is provided at 5 v.
We can do better!
I know from experience that AA is great.
They are cheap, high power, very low internal resistance and are easy to buy anywhere.
9 v has 500 mAh (
A total of 9*500 = 4. 5Wh power)
There are 2*1 in total for two AA, each with 3000 mAh.
5 V * 3000 mAh = 9Wh, the power is about twice the original.
The only problem is that 2 x AA provides 3 v and what we need is 5 v.
For 9 v batteries, we can use a linear regulator because 5 v is greater than 9 v, but sadly we can\'t turn 3 v into 5 v using a linear regulator.
Instead, we need to use a boost regulator (
Also known as DC/DC switch/step-up regulator)
The process of how Boost regulators work is a bit beyond the scope of this document and it can be said that they work well, but are more annoying than linear regulators because you have to pick an inductor and connect some extra parts.
You can get more information about Boost converter on Wikipedia, which is where I steal boost topology images.
So at this point I started thinking about the shell and the size.
Most people think this is the last one. it\'s a bad idea.
If one thing I learned from hacking into electronics is that you should try to select this case first because it determines a lot of electronics and interfaces.
I know the parts of the kit have to go through all-hole (
No surface mounting)
And easy cooperation.
I also want AA batteries, the 2 th is fine, although I know from experience that most boost converters can use any number of the 1 th and 3 Th.
I have a preference for Altoids cans and I also know that I can ~ 2 AA put in the mouth candy jar so I took out a can and did some measurements.
OK 2 AA fits well so now I flipped through the battery stand I collected and found one (PCB-mount)
It seems to be fine, it doesn\'t have a switch, but I don\'t need a switch (
See exact calculations later)
So I made some measurements. . .
It looks like I have about 1. 25\" x 0.
Semi-circular PCB space at the top of the board.
I also tried another battery stand which gave me more space, 1. 25\"x0. 85\". . .
But the battery is horizontal, so people have to remove the stand in order to replace the battery.
I hope you can take them out directly so I don\'t like this one (
I don\'t need extra space either as it turns out)(
I\'m doing a little hack right now to turn the PCB mount 2xAA battery box into a wirelead one.
Basically I just weld on the 6 \"wires in red and black and pass-hole leads.
This is actually a bit difficult because the plastic will melt and you have to keep it in place when you weld.
Not recommended :))
Now that it\'s done, I\'m ready to think about what I can cram into that space.
The next step is to select an inductor.
This can be a bit painful and you can throw a lot of math knowledge on this issue.
However, the data sheet suggests (
Under \"inductance selection)
Use ~ 1 Get an inductor of 22 uh.
2A saturation limit, DC resistance 0. 02 ohms.
What we want is through
Holes, which actually means that it is difficult to find the inductor;
Almost all the inductors are surface mounted.
But I\'ll see what digikey can provide.
I search for \"fixed eh inductor ~ Smd ~ Smt \", which means I don\'t want SMT/SMD (surface mount)
I want a non
Adjustable inductor in The uH range (not mH or nH).
Then I use 1-
3A current and 18-Inductance.
It filters out about a dozen options.
The SLF inductor is actually surface mounted and we will completely ignore the inductor that costs more than $2. 50.
The inductor for a small electronic device like this should cost about $1.
$2 as guideline.
That leaves dn74 18-
ND \"inductor 27UH power axial\" and 6000-220K-
RC \"inductor HI current radial 22 uh.
\"Both look good, about 1.
5A saturated current and 0.
07 Ohm DC resistance.
I also checked the trade.
The online search for trade is not as good as Digikey, so I finally looked at the paper catalogue.
I only found one inductor, really, 18R223C (
Radial power inductor)
And/or 18223C (axial version)
This also has enough power capacity and 0.
03 Ohm DC resistance.
So, 2 per order.
What I actually did was go through the Digikey directory where I only found the dn74 18 inductor (
The other is hidden in the RF inductor section).
It showed up before the Cesar box, so it took me an hour or two to make a prototype.
The circuit itself is simple, I want a large electrolytic cover for low frequency smoothing of the battery and an output cover pair (
High frequency electrolysis and ceramic caps. smoothing).
I also need the chip, reference voltage capacitor, inductor and diode in order to complete the boost regulator.
I happen to have some 1n5818 which is often used as a schottky diode in a boost regulator.
Of course, I also need a USB Type A female Jack with two holes to weld the battery pack.
Keep in mind that the chip has an internal transistor switch, and you can compare the schematic diagram to the topology diagram in step #3.
All of these components must be installed in the remaining space of the battery pack.
I have the inductance, patch of the EagleCAD library part (
The rest is already there)
Then spread the board out.
I will not make library parts in detail in eagle or pcb layout and others have already done so.
Using any software you want, I like Eagle because there is a free version to download if you are just making small pcb.
Since I know this is just a prototype version, I made the PCB single side-
Easy etching.
I also have a lot of marks.
I print out the paper version of the PCB and punch the parts to verify that they are the correct shape/packaging.
I put my etching device together, open the heater of the etching slot and print out a bunch of tiled PCB layouts on the toner transfer.
I transfer the toner to a single sided PCB and etching in the water tank, then clean the toner transfer and drill holes with dremel drill bit
Press with a carbide drill bit and cut out the shape.
Then I weld the part inside and put it in the shell with a double battery
Double sided foam tape, hold and hold the battery holder and PCB without short circuit the PCB to tin metal. OK, done!
Now let\'s test if it works!
There are two batteries inside and I measure the voltage on the USB connector: about 5 v which is good.
I sent this version to friends with one of each iPod, including the latest 4g video iPod
World Test: verify if the iPod will charge and how long it will run with the extra package.
Now is the time to verify efficiency math: How good is it after all?
Therefore, in theory, we should be able to calculate the efficiency of the boost converter from the data sheet information.
We basically improved 2. 5-3VDC -
> 5VDC, about 50 mA-100mA.
Check the MAX756 Data Sheet, please note the efficiency chart.
Therefore, we should improve the efficiency by about 85%, maybe a little more.
I think the only thing that can change this number a little is the inductor. (
Below I verify my efficiency is 82%)
If we get a 82% efficiency conversion from 2x3000 mAh Duracells, that means we get (2 * 1. 5V)* 3000mAh * . 83 = 7. 38 Watt hours.
Compare it to a single 9 v we previously calculated :(1 x 9V)* 500mAh * . 65 = 2. 93 Wh.
So we got about two.
The power consumption of these two AAs is 5 times higher than that of a single 9 v.
With rechargeable batteries, we2 * 1. 25)
* 2200 mAh * 81% = 4. 45 Wh (
About 50% more than alkaline 9 v, 3 times more than rechargeable 9 v)
Next, let\'s use the test equipment to verify the efficiency and try different inductors to see if they are different.
Instead of using the battery, I offer 3 v from the desktop power supply, which will also tell me how much current is consumed.
I will replace the iPod with resistors.
Since the standard USB current is from 5 v to 100 mA, that means I need a 5 v /.
1A = 50 ohm load.
I can\'t use only one small resistor because of 5 v.
1A = 1/2 W, 1/4 W for most resistors.
So I screwed together the big \"power\" resistors of the two 100ohm.
I also checked the resistors to verify that they are 50 ohms together.
I also found a power resistor of 20 ohms.
This will allow me to test not only the 100 mA load but also the 250 mA load.
I did 4 tests with two inductors: the load on the two was 100 mA.
5 V in and 3 V in (
Rechargeable and disposable batteries)
There is a load of 250 on both.
My results are summarized in the attached table because the second image looks like the inductor #2 is more efficient, probably because it has a lower DC resistance (
30 milliohm instead of 70 milliohm for other inductor).
It\'s a little cheaper, so I use that inductor.
Anyway, it looks like the efficiency is about 82%, which is about the same as I expected.
Another thing to note is that I don\'t set the on/off switch as you need the 9 v 7805 regulator.
This is because the static current of the MAX756 is very low, about 100uA (0. 1mA).
I tested it myself, about 75 ua.
This means that the self
The discharge rate is about 2000 mAh/0.
1 mA = 20,000 hours for more than 2 years.
Most batteries don\'t last that long!
So when there is no power supply plugged in, we don\'t need a switch and almost no power supply. (
Finally, I found another radial inductor that is cheaper and more efficient, which I used in the kit)
So now that I have verified that this project works, I have to figure out if I want to sell it, how much I want to sell, and how much I want to charge.
Many people have different technologies for this.
I tend to use my \"gut\", which usually means I use a lot of information, but it\'s hard to express it.
I tend to decide if I want to sell something based on how popular/useful/easy it is.
I think this kit will be very popular and useful as a lot of people have something to charge/charge via USB.
Also, it seems that other people are selling something similar (
For example, a 9 v 7805 charger, or a 9 v charger for Griffin, or a 4 x AA charger for Belkin)
Because all the parts passed, it was easy to make
They don\'t have many holes.
I basically assume I will sell around 200 in a few months and I will order 100 of the parts in bulk, so I should do that. (
As I will show later, due to the economies of scale in PCB manufacturing, I often buy more than 100 PCB at a time. )
So far, I can sell a kit for hundreds of units in a few months, especially if it\'s bought by a blog or website.
This may or may not be true for you, but if you can\'t produce 25 kits at the same time, you\'ll find it hard to make any money in the process.
To figure out how much to charge, I made up a table with different quantity price to calculate PCB cost, I used insta-of advanced circuit-quote service.
These prices are 2 PCBs and I will cut two because it is cheaper (
Probably because they don\'t like to deal with very small boards).
I usually go for two weeks.
Please note that the PCB quote does not include $150-
Time tool NRE fee, $3 added in/50 price, $1.
Price from 50 to/100.
Advanced Circuits are a bit expensive, but they are of excellent quality and good at catching errors.
You can try to go to a cheaper store anyway, but I can only guarantee for these people.
Shipping charges are also included, probably $1 per piece.
In general, in order to calculate the \"retail\" cost, I doubled the cost of parts.
In this case, I will charge $19. 50.
Anything below $10 or $20 is great as $20 is considered a coupon for things/food.
There is more work to be done.
First of all, I redesigned the circuit board because I am going to use a radial inductor instead of an axial inductor.
I actually did another etching test and verified everything for the last time.
Then I put two boards together. cheaper)
And gerbers. I use gerbv (free software)
Used to view and verify gerbers.
On windows, I use GC-
I always check the motherboard with www. freedfm.
Before I ship them out. I used 4pcb.
So this is the same company, but even if you don\'t use 4 PCB.
This is a neat service as your PCB manufacturer. A week later (
Depending on your turn)
A box is displayed on the board!
Then I sat in front of the computer and did a lot of website stuff.
I also took a lot of photos.
Good photo setup will make the document easy.
I have a simple 150 W ECT bulb diffuser setup in EYEBEAM.
The key is Tripod!
Okay, you got the equipment.
How did this build it!
Organize the tools first.
There are several components needed for the tool.
None of these tools are included.
If you don\'t have them, now is a good time to borrow or buy them.
They are very handy whenever the electronics are assembled/fixed/modified!
I provide the link to buy them, but of course you should get them in the most convenient/cheapest place.
Many of these parts are available in radio sheds or elsewhere (higher quality)
DIY electronics store
Next, you will need to put two electrolytic capacitors C2 and C3 together with diode D1.
Make sure to align the white stripe on the diode with the white stripe in the picture on the board.
There are also white stripes on the capacitor, making sure they are arranged like the picture on the left.
When you put the part in, bend the wire a bit so that when you turn the part upside down and weld it, the part will lean against the plate.
The first step is to weld the kit together.
This tutorial is great if you have never welded before.
If you\'re part of a new streamingvideo-
A generation, this set of pads may be helpful to you.
Make sure the iron is swideg.
Touch the tip at a 45 degree angle, make it heat the hole/ring and lead wire, and then touch/poke the solder with another hand.
Clamp the lead with a diagonal cutter.
Be careful, the clues won\'t fly on your face.
Cut off the wire where the solder joints gradually become thinner.
Place two yellow ceramic capacitors C3 and C4, power inductor L1 and USB jack.
Like other capacitors and diodes, there is no polarity in the capacitor and inductor, so don\'t worry about placing it backwards.
Weld these parts too.
When soldering a USB jack, make sure to put a lot of soldering in two large side holes: they are mechanical connections to the jack.
If you don\'t make a good solder joint (
Fill in the hole completely with solder)
Jack will collapse in the end!
So do a good job.
Clip the extra wires here too.
Do not clip the USB jack leads: they are in the right size.
Place the 8-pin socket next to the Jack, just like the screen printed image on the PCB.
Also put in the wires of the battery pack and make sure not to mix them together!
The red wire is in the corner.
Solder the pins of the socket and the two wires.
If they seem to be slipping out, you may have to press them down the board from below.
OK, insert the MAX756 boost chip so that the small gap in the chip matches the gap in the socket.
Make sure it is in good position: press hard to make sure all pins slide directly into the socket. You\'re done!
Now that it\'s built, it\'s wise to do some small tests to verify if it works properly.
You need a multimeter with continuity testing and voltage measurement, each with one.
Read the manual and verify how to get into the mode you want.
OK, now you can put it in the box.
You can go buy a can of Alit gum and eat it or send it to your friends.
I find them disgusting so don\'t send them to me.
You will need the MintyBoost kit, an empty sugar jar, a pair of Tintin and two double sided foam tape (
Tape included in the kit).
Cut two gaps at the end of the tin, just where the flat part ends, the tin starts to round.
Now you want to bend the cover back and forth to break it, you can bend it over if you are careful, which will make it a jar with a sharp edge missingTry a test fit.
Slide the board in first, then put the battery pack in.
Don\'t put the battery in this test!
The circuit board may short circuit and destroy the circuit!
Once you\'re happy, remove the electronics and place the double-sided sticky foamtape on the board and battery box.
The tape keeps the board in place and prevents the pins from short-circuiting relative to tinYou. You may have to push down as soon as the battery holder enters to \"pop-
A little out of the \"bottom. . .
Otherwise the case will not be closed. That\'s it. . .
Go ahead, come on!
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