View Full Version : Propeller-based DC-AC inverter (my own On-Line UPS)
11-17-2010, 08:50 PM
I am planning on constructing the On-Line (meaning always active) UPS based on the Propeller 1 P8X32A microcontroller for active power supply driving and monitoring. I may need two if necessary. But Here's the question, should the main function (such as driving the Noritake / Itron 7000s VFD to display what's going on in there, monitoring the higher-peak-ampere Lithium-Ion [or Lead-Acid] battery as it's on active mode [when the AC mains drops out], and to condition the power [ex. Converting DC voltage rail powers into superimposed-PWM sinusodial AC powers] - and the likes) be really seperated into few Props with different firmwares?
But why build my own UPS? Quality dispute, I shall say. I don't really trust few UPS anymore as it can cause expensive damage to the hardwares. Also, "why not get away with sawtooth or square waveforms? They works equally well." Hard answer is NO. I already taken reactive / inductive loads into account - like "What if I wanna plug a box fan in? What about the equipment with the boat anchors (like HP printers - they uses iron transformer)?"
11-17-2010, 09:40 PM
I don't really trust few UPS anymore as it can cause expensive damage to the hardwares.
I have never had a UPS casue any damage .
one ole APC I had put nasty AC Trash on my TV . but thats to be expected
Note I HATE UPSes . most of our devices run at 12V and below why not inject it right at the rails and not waste it on 2 !!! transformers and related gear ..
that said I use TrippLight APS series with BIG external batts.
""plus efficient PWM sine wave AC output i"" not that NASTY consumer modified 4 step sine wave trash ..
as for a Prop baased UPS . I say go for it !!!
One word of a advice . layout for the HI AMP 12V section will be a bear . I was makeing a 1000A+ speed con for my college and it was a good learning experince in how to wire big FETs . short leads are first and formost on the TO-220 pacakge the leads Fused open while the FETs were ice cold . IR has a few Sweet Fets that are VERY good at Hi AMP service .
I would use the Tab on the TO-220 as a lead not the middle lead this way you can solder Very close to the package a WIDE copper rail to each FETs lead ..
11-17-2010, 10:21 PM
I have been playing with this "propeller driven inverter" idea for a bit now, the current experiment is to use a standard off-the-shelf Class-D power stage (TI TAS5631, 600W @ 50VDC) and use the Propeller to generate the sine wave in digital form to be outputted to a TI I2S-to-PWM controller (TI TAS5012, 192kHz@24-bit, 3.3V-IO). A transformer steps-up the voltage from 50VAC to to 150VAC (1:3), and the Propeller controls the TI PWM controller's volume register to calibrate the output voltage. Only takes 6-pins for the whole thing. Filtering before the transformer kills anything above 120Hz, so the output is essentially cleaner than wall power at 120VAC/5AMPs.
If you want to do your own UPS, look into the newer "80+" GOLD and PLATINUM ATX PSUs, they are designed with a zero load output on a signle 12VDC supply (you can tweak the sense votage to get charging voltage out of the supply). They also feature Power Factor Correction to near perfect current waveforms (95%+). You can use the ATX supply's "power good" signal to switch to battery power.
Propeller should be overkill for this :)
11-17-2010, 10:30 PM
Yea. That's a good point, I still have crappy 150W inverter and it made funny squiggy lines on LCD TV, since it spat out square waveform. However, that's definitely BAD for air conditioners (very few are made with BLDC R134a compressors, so it's basically like playing Lottery).
And, yes, I knew what I should do with that things that would have to deliver 100V Japanese voltage and 120 V American voltage (I would be able to alternate between voltage on the control panel - they use same NEMA outlets, anyways. Oh yea, very few Japanese business / house has 3-prong outlets, so I am going to put one in as an insurance. Ground is good! Hot is bad!) - yea, 100 - 120V at 20A.
I should beef the rail up just in case it decides to go BANG! It would have to have A LOT of sensors for overcurrent protection (and throw in circuit breaker for luck). However, being an On-Line inverter, the voltage fed in from the outlet should have no effect on outlet voltage unless something in it screws up and the bypass bar relay switch kicks in.
However, I have been considering the BATTERIES... I decided to go with Lithium-Ion (LiFePO4) battery since the size I picked out, 32900P, is good enough for me (90A peak discharging current), so it would allow me to either run my computer long enough during power outage or to buy me some time shutting a workstation (with a HUNGRY SMPS) down without having to endure the data loss.
BTW, Yes. I have been thinking about using a computer power supply - all I can say, it would be nice for battery charger. Maybe for DC rail, I will have to find out eventually.