NOTE: stretch goals 1 and 2 were "kind-of unlocked" by a tiny redesign of the PCB. Have a look at the campaign update #3 for details. They remain listed here for the sake of completeness.
If we reach 2500€ by the end of the campaign we will produce a second variant of the PGCPSU with a lower set charge current (1.3A or 1A instead of 1.9A). We'll let you choose which one you want (except for the already made Boost PGCPSU in the Super Early Bird reward). In order to make it easy to differentiate the two we'll choose another color for the solder mask. - UNLOCKED / by CHANGE
At 5000€ we will ship a set of current sense resistors (three or four values for like 1900mA 1000mA 650mA and 400mA - exact values may vary depending on parts availability) so you can choose which one fits your application best. Note that modding this will require you to solder a 0603 part, so it might not be up to all of you. - UNLOCKED / by CHANGE
At 10000€ we will expand the "free Boost PGCPSU" to all pledges. This means that every reward containing 1 PCGPSU DUO will get 1 free Boost. For the More Fun rewards we will add 2 free Boosts and the So Much Fun backers will get 5 free Boosts.
Getting into embedded electronics has never been as accessible and easy as nowadays, yet many things are still hit-and-miss, especially when going the cheap route. Even basics like choosing the right power supply for your latest battery-operated project can be super tricky. With the Pretty Good Cheap Power Supply Unit, we're solving that problem for you!
PGCPSU is a three in one power supply board: it integrates a lithium battery charge management circuit with 5V and 3.3V DC-DC converter-based output rails to power most projects in a very compact form factor. We took special care in selecting inexpensive yet well-fitting parts to make up for a great little power(ful) supply!
Here's what you get:
- no surprise: PGCPSU is fully specified
- 5V output rail providing at least (*) 350mA
- 3.3V rail providing at least (*) 400mA
- low quiescent current (49uA for the 5V rail + 57uA for the 3.3V rail)
- enable/disable pin for the 3.3V rail with selectable default state solder jumper
- micro USB input or pin header for charging (4.7V to 6V max.)
- high efficiency even at low load (important for great battery life!)
- small / tiny with only 25x20mm
- good line regulation
- quick charging at up to 1.9A (fully charges our awesome 2600mAh cell in just over 2h!)
- integrated battery protection (including reverse polarity protection!)
- good fault tolerance and recovery behaviour (over-discharge, short circuit/over-current etc...)
(*) you can draw the indicated current over the full range of the battery charge while still getting a clean output voltage, so we're not talking about the usual best case "up to" rating (which would be up to 650mA on 5V and up to 800mA on 3.3V for our board). Due to the way the PGCPSU is built (have a look at the block diagram right below) you can't draw the maximum current on both rails simultaneously however.
What can you do with it?
The limit is really your imagination here - and physics we guess... Here are a few things we tried (everything with a 2600mAh cell):
- Running the Arduino Blinky sketch for 3,5 days (or over 25 days with a bit of tweaking like removing the power LED, disabling the USB-UART, bypassing the LDO, using sleep states etc....)
- Running a Raspberry PI Zero W posting its uptime to a REST API via WiFi for 17 hours
- Running an ESP8622 based soil moisture and temperature sensor for ... well it's been running for 4 months now, posting a measurement every 10 minutes
- ...same for an ESP8622 based WiFi / PIR motion sensor
- Using it as an uninterruptible power supply for an Arduino based test data acquisition system (not ideal for the Lithium cell for sure - but it works superbly)
DUO super early bird (only 20 units):
We can get these out super quickly as we have all the bits and parts already. The free "PGCPSU Boost" is the same PCB, just with the 3.3V part unpopulated (these are already built - sitting in a box and waiting for your pledge).
First batch DUO (only 30 units):
Be among the first ones to get your PGCPSU. To build these we have to order PCBs and some parts, which can take a week or two, manufacturing and shipping these out should be a breeze and happen very quickly after the end of the campaign.
First batch DUO starter KIT (only 30 units):
You'll get your PGCPSU out of the same first batch! Additionally, you will get one of our amazing 18650 2600mAh Lithium cells with the right connector. This makes it a plug and play experience - literally!
We're still looking for affordable overseas shipping options that are willing to carry Lithium batteries. So, this reward is for mainland Europe / EU only at present.
One DUO, More DUO fun and So much DUO fun:
Get 1, 3 or 10 PGCPSUs in one package. We will send these as production goes after the Super Early Bird and First Batch rewards are out.
The KIT editions of One DUO, More DUO fun and So much DUO fun:
Get 1, 3 or 10 PGCPSUs in one package with the matching count of our amazing 18650 2600mAh Lithium cells. They have the matching JST-PH 2-pin connector. Start your projects right away!
As with the First batch KIT reward, we're still figuring out the overseas shipping options. For now: mainland Europe / EU only.
How does it hold up against X?
We can't really test every contender, but we did some shopping and put together a comparable (both in cost and features) setup:
On the left: one PGCPSU DUO
On the right (bottom to top):
- a lithium charger based around a TP4056 and DW01A protection IC
- a "600mA 5V out step up" converter labeled HW-553 (we unsoldered the useless power LED drawing another 5mA btw)
- a step down converter adjusted to 3.3V out labeled MH-MINI-360
In terms of efficiency the PGCPSU is far ahead of the random module combo in every way. Especially on the low load end. The quiescent current of ~100uA vs 11.44mA is making the difference! This means that you could leave a PGCPSU attached to one of our lithium cells for over a year and it still would hold over half its charge after that. On the other hand, the battery would be fully depleted in under 10 days with the other combo. An that's doing "nothing".
At higher loads the difference is not that staggering and, in some constellations, the HW-553 can actually provide a few milliamps more current before dropping out.
As you can see, the PGCPSU has a much more stable voltage output over the full load range on both output rails. The unstable 5V out of the TP4056 combo in the cell voltage range below 3.2V were an issue for loads like the Raspberry PI Zero W which are more sensitive to supply voltage fluctuations.
Roughly twice the charge current, means that your devices will be topped up super quickly. Surely, at 2 Ampere the PGCPSU gets toasty, but competition does not stay cool in any way either.
To give you a feeling of the difference here's a time lapse video (over 4h in just 47s):
The PGCPSU generally has pretty good ripple and noise figures (measured with an oscilloscope, configured to 20Mhz bandwidth using a 1x probe). The cobbled-together boards show varied results. While the 3.3V rail is nice and clean, the 5V rail is falling far behind with noise ripple and noise rising to a worrying level above 100mA load.
The last test category is not in a chart: fault tolerance. The PGCPSU behaves as designed, recovering well from short circuit (even sustained - we tested 3h) on all rails. The TP4056+ combo behaved badly when shorting the 5V rail - requiring to un- & replug the battery in order to recover from the over-current protection. Oh, and we killed the protection IC on the TP4056 LiPo charger as well as the 5V step up converter during our reverse polarity test.
The conclusion here is: you're almost always better off with a PGCPSU! At least as long as you're happy with the possible current supply figures. But really 350mA/400mA across a full battery charge is plenty for battery powered things where you target long battery life!
What's that awesome 18650 cell?
It's a carefully selected 18650 battery with true 2600mAh capacity. It's made by a reputable Chinese cell manufacturer and we're using it in another product of ours. If you don't have a cell that can deal with nearly 2A charge current, we recommend you to get one. The KIT pledges include these.
The cell has its own protection circuit, so even if you end up using it without our tiny PGCPSU, it has your back covered ;)
Things we still have to do
- a nice and polished datasheet
- buying parts and other supplies (packaging)
- build, pack and ship your rewards
- figure out a viable overseas shipping option for the Lithium batteries (no guarantee there :( )
- depending on the number of bakers: building a small pass/fail test rig to be able to sustain a 100% test rate
Things that are done
- Thoroughly test, measure, use and abuse the PGCPSU
- Panelize the PCB and program the pick and place machine
- Build a few boards (29 to date, some incomplete)
Staudt Technologies was founded in 2018 to manufacture and commercialize a small designer LED nightlight-type product. Among the many pieces of equipment we bought to that end was a mid-range pick and place machine, which was a totally new kind of production machinery to both founders. To keep the cost of the learning curve as low as possible we decided to spin a "quick'n'cheap" board to learn to program our P&P machine.
The PGCPSU is simply the second iteration of that board, where we crammed all the components as tightly together as possible to make it not only useful and good but also tiny!
The different circuit stages were borrowed from older projects, where we used them on their own. They were good then and together they make up for an excellent little power supply board in our opinion!
Risks and challenges
This is our first Kickstarter campaign, so we're learning that as we go. As with all projects, Murphy's law applies, so unexpected things may happen, and some delay may occur. But we're confident to be able to keep up with the indicated delivery times.
We're very confident about the hardware and the manufacturing process as - save for parts procurement - its fully in-house and well controlled. The bigger risk is getting the rewards shipped to you in fact. Shipping in the EU will be executed by Deutsche Post and DHL most probably as we already use them. We're currently sorting out the options for the rest of the world, with DHL being the preferred although sometimes expensive options.
On the parts sourcing side, we may hit some lead times with our battery supplier depending on the number of KIT orders. We always have a few hundred cells on stock, so we're probably safe, and we're talking weeks, not months there anyway.
In any case we will do our very best to avoid or mitigate surprises and always keeping you informed.Learn about accountability on Kickstarter
- (30 days)