Akom's Tech Ruminations

I have an ancient APC Smart-UPS 1400 RMNET. It's a very nice UPS, but I have frequent multi-hour power outages and battery life becomes a problem. I have these issues:

1. Short battery runtime, especially as batteries age
2. Lead-acid batteries require frequent replacement and quickly lose capacity (and there are 4 of them)
3. UPS will not accept 110v from a cheap generator (mine is a 700w). This means that I can't do a live power transfer from mains to this generator, and I have to reboot everything to switch

So, I had a few ideas

• What if I could feed externally-generated DC battery voltage directly to the batteries? For example, via a generator powering a AC-DC power supply
• What if I could substitute Lithium batteries for Lead-Acid? LiFePO4 would be ideal in this application because weight doesn't matter but the long cycle life does. A 4S pack would have a similar voltage to a 12v lead-acid battery

Continue reading "Adventures in Modifying a UPS for external DC power and LiFePO4 batteries"

Disclaimer: It is perfectly legal to program an odometer to represent the correct mileage for the car.

Problem:

The car is a 2006 Nissan Sentra 1.8S. The instrument cluster is faulty and flips overdrive on and off at random. I ruled out the rest (switch, TCM). Thus, the cheapest option is to swap in another cluster, but that means that my mileage will be wrong. The replacement cluster I picked up on Ebay has 24K miles. Mine has 181K. Slight difference there.

Solution Summary:

Use an EZP2013 IC programmer to read the memory from your old cluster and write that to the new one. Clearly this assumes that you are still in possession of your old cluster and that its EEPROM is intact.

Solution Detail:

Continue reading "Odometer Reprogramming - Nissan Sentra"

Although I wrote a somewhat harsh review of the PetSafe Simply Clean Litterbox on Amazon, I still felt that there was some potential to this thing. What I wanted most from it was a very low maintenance experience, and having to empty the waste bin every 3 days simply didn't seem to qualify. When I go on vacation (and please don't start a neglect flame war over this) I leave the cats alone - monitored by 4 cameras, auto feeder, 5 gallon water dispenser and many litter boxes. I don't want to bother relatives with the long drive to come over just to clean cat poo, and my cats do not take well to being moved. Or to strangers. Or to basically anything besides the quiet at-home life that is exactly like yesterday.

Therefore, what I'm looking for is a larger waste bin. The litterbox doesn't handle capacity problems well - it backs up, jamming up against the chute cover, making a mess and eventually just shutting itself off. What I need to do is to create a jam-resistant path for the waste to go, somewhat like this patent here. The idea is good but it seems a bit too complex for my taste, and of course it is intended for a rectangular raking box like the LitterMaid. So, I chose to do the simplest and most reliable thing I could think of.

Continue reading "Increasing capacity of the PetSafe Simply Clean Litter box"

Apparently if you have the power-on self-tests set to "Minimal" or "Fast" or anything besides the "Let's check everything for 5 minutes every time the machine boots", you'll have a brick with a blinking CAPS lock instead of a laptop once you upgrade memory.

The only way I found to fix this (other than clearing the BIOS) was to put the old memory back in, go into BIOS, and enable thorough self-test. With that on, the laptop notices the memory size change and does not freak out - merely tells you about it. Once you're done you can disable the self-tests.

(I experienced this on a Dell Precision M4400, but googling seems to indicate that this affects the Inspiron and Latitude lines as well, probably others).

The instructions that come with this little gadget are priceless in their verbatim Chinese glory, but are not helpful in their vague "Leave the details as an exercise for the reader" approach.

Here are the exact detailed steps to actually set the clock

Continue reading "Setting the date/time on the Mini Keychain Spy Camcorder"

I've had my D945GCLF (the Intel Atom 230 board) up for 440 days. That's an impressive uptime until you realize that it's a Gentoo box running asterisk, mpd, and not much else. As anyone familiar with D945GCLF or D945GCLF2 knows, the northbridge has an aluminum heatsink with a 40mm fan. Most people have had theirs fail right away, but I was lucky enough to have mine last over a year before starting to vibrate and slow down. Once I started getting Nagios alerts about high temps, it was time to do something.

I never liked the idea of small fans. A 40mm sleeve bearing wonder is certainly no exception. When it comes to cooling, I always look for big and slow - and that in my book means 120mm running at 7V speeds. I looked for a replacement fanless heatsink but couldn't find one that was reported to fit. Here is what I did:

Continue reading "D945GCLF fan issues and alternatives"

I have a Dewalt 18V cordless drill, which was very expensive ($200 back in 2001), came with two batteries (heavy, NiCd packs), and I've used it extensively for just about everything when we bought our house. Now both packs are dead. I do maintain them well, as nearly 7 years is much longer than their expected useful life. So I checked out the prices - and the packs are over $80 each! ... Seems a bit expensive for a bunch of NiCd's in a nice (tough, indestructible, convenient) plastic package. I looked at NiMh cells... but then using the original charger becomes questionable (probably cannot), plus the cost of 12 cells is almost $80 in itself - not to mention soldering 12 cells together, myself??? I don't think so....

Then I thought about LIPO cells... Let's see - 18V, that'd be a 5 cell (18.5V)... Well, for a test, I figured I'd try what I have around, and what I have around are 3 cell packs.

Continue reading "Replacing NiCd power tool batteries with RC LIPO's"

The Motorola HS850 was a very popular bluetooth headset in its day. A lot of people seem to complain that their HS850's gradually develop one of the following symptoms:

• Dials/hangs up, randomly
• Redials on its own, randomly
• Hangs up or dials at the slightest touch or handling of the unit

This is what is most likely causing the problem:

Continue reading "Fixing Sensitive Button on Motorola HS850 bluetooth handsfree headset"

I have a hand-me-down Garmin C330, the el-cheapo, no-text-to-speech teletubby-looking GPS unit that every online store was liquidating a few months ago. Mine also has a dead battery, and while it used to run for 1-2 minutes on it, now it barely runs 5 seconds. I can live with that, after all - you generally use it while plugged in, but it is oh-so-handy to be able to hand it to the passenger for co-pilot... co-piloting.

So, I had to do something...

Continue reading "Replacing Garmin C330 Li-Ion battery on the cheap (with whatever is onhand)"

Last week I hacked up my RC transmitter and added a Dual Rate switch

See here: (How I hacked it up).

I thought I was so cool for adding two wires, one toggle switch and two drops of solder to an RTF transmitter (oh and a nice hole too). Well, everything worked great on the ground, but once I actually flew the plane, not all was well - the control range dropped to about 60 feet!. I didn't connect the dots at first and thought it was a broken antenna wire or something, or a new flying site (coincidence). Nope.

Apparently, adding two thick wires radomly into a complex circuit and placing them along the perimeter of the case can have some unexpected results. I took the wiring and the switch out, and all is well again, control range is longer than sanity permits me to test (plane is a dot in the distant sky, but still seems to be controllable).

Continue reading "Not all that is hackable should be..."

I can't say that I have a good reason for doing this, other than the potential for letting inexperienced family members fly my plane, but I thought this should be easy enough to do:

The RTF transmitter that came with my Pitts S2A has a bunch of dip switches, which are not so quick to flip on the fly - and I've played with friends' real professional transmitters - and they have what seems to be useful toggle switches to control this stuff. So I figured I'm gonna pretend that I'm cool too.

The transmitter turned out to be very neatly designed, and finding the switch and soldering a pair of wires was surprisingly easy. Moreover, the cute silver pads on the top corners of the transmitter are actually silver stickers, covering up pre-drilled holes intended specifically for what I'm putting in there - a toggle switch.

Continue reading "Hacking up RTF RC Transmitter with a Dual Rate switch"