Jack Crossfire's blog View Details
Posted by Jack Crossfire | Sep 18, 2016 @ 05:32 PM | 1,991 Views
The ganged batteries made their debut 18.6 mile drive. Speed was reduced to 9:30 on account of the heat, which translated to 10:00 after PWM errors. The fuse didn't heat up. After the drive, both batteries were cold.

It was quite luxurious to not have to stop the run, squat, & change batteries. You have no idea what a pain that was for 1st 3 years of robotic exercise coaching.

Battery #2 in the low tray took 4545mAh. Battery #1 in the payload bay took 3294mAh. So they discharged as expected, but it was a quite high current draw. They carried water for 7.5 miles with 5 miles uphill. Need to swap battery trays to see if it was cable loss or internal resistance.


The wiring was redone to handle more current & gain a fuse. The fuse in the apartment was a polyfuse which started blowing at 3A. It was delayed proportional to the current. 3A took a long time. 8A blew it almost instantly. It got hot, never cut off, but allowed a current below 1A after blowing & continued heating. It would probably explode if the batteries shorted, but it's better than the wire bursting into flames. An HRC fuse would be nice. The normal cruising current with 2 batteries is 1.2A - 1.7A if they're balanced. It might blow on a hill or if the human goes real fast.

The once dubious LED arrangement turned out pretty respectable in its ability to light a large area.

The attempt to glue the wheels failed. The rubber flexed. They instantly popped out of the glue & spun the same as before.
Posted by Jack Crossfire | Sep 16, 2016 @ 11:11 PM | 1,926 Views
Suspect because it was a terrorist attack, the cause of the last Falcon 9 explosion won't be disclosed until after the election & H-Rod already had the talk with Musk Rod, for his sake. It'll be quite the stir when he finally reveals it right after H-Rod's election, but maybe Americans will just think it was politically correct for ISIS to blow it up. More of a stir would be if Emirates, Quatar, & Etihad airlines immediately got into the space tourism business, just like how the Islamic airlines took over the industry after 9/11.


In other news, I was intrigued by the fact that the fictional New Bezos would be larger than the fictional Musk Heavy, yet would make 1.5 million lbs less thrust. Musk's strategy was always to clear the tower as fast as possible. Every second of the liftoff burns enough fuel for 9 seconds of the landing. So he puts out 2 million more lbs of thrust than the weight of the rocket.

The liftoff mass of New Bezos was never given, but it would be comparable to Musk Heavy. A lot more propellant would be burned to clear the tower, so all that size would probably end up giving the same payload capacity as Musk Heavy.

7 Bezos-4 engines would make 3,850,000 lbs of thrust. The Musk Heavy would make 5,200,000 lbs of thrust to hurl 3,200,000 lbs.

New Bezos would offer a much bigger payload fairing. The payload volume on a 3 cored rocket is the same as 1 core, limiting the benefit to manely higher orbits of the same payloads or...Continue Reading
Posted by Jack Crossfire | Sep 15, 2016 @ 01:01 PM | 2,253 Views
It was a white knuckle experience to gang the batteries for the 1st time without polarized connectors. The batteries were chilled to reduce the maximum current. There was a brief sensation of heat which went away. 8.9 miles later, battery 2 in the undercarriage took 2220mAh. Battery 1 in the cargo took 1222mAh. They ran for 87 minutes.

Suspect the higher internal resistance of battery 1 prevented it from discharging as much as battery 2. Battery 2 would have eventually run out enough for battery 1 to supply most of the current.

The balancing tab was always the easiest way to gang batteries, but with the risk of reverse polarization. A fuse is highly recommended. The mane problem is the surge current when accelerating. The fuse might go for too long for battery 1 to supply any current at all.

String held battery 1 in quite well.
Posted by Jack Crossfire | Sep 13, 2016 @ 01:23 PM | 1,678 Views
With a pile of LEDs from the Radioshack sale, it was time to upgrade the lighting. The lighting could be doubled without increasing current, by shuffling voltage regulators.

The lighting would now drop 7V across 2 LEDs. The trick was using a different plug to prevent plugging 7V into the status LED & to prevent the glitches which plagued lighting before. LED voltages ended up disappointingly uneven. The white ones varied from 3.4 to 3.6. The red ones varied from 1.9 to 2.2. Any attempt to go higher would put some white ones at 4V. It's tempting to put them all in parallel again. It would double the current from 80mA to 160mA.

There was an unused 3V regulator on the board. That became the mane electronics regulator. The 1st test lasted 3.6 miles before it overheated. The XBee used too much power. The next step was to feed it from the 5V regulator to dissipate the heat better. That got it down to 50C....Continue Reading
Posted by Jack Crossfire | Sep 10, 2016 @ 01:59 AM | 1,632 Views
Given the time he had to review fault trees, that puts the needle strongly at a terrorist attack. Given the cause of almost every single explosion, plane crash, & mass shooting in the last 8 years, it's the simplest answer. This explosion was too energetic from the beginning to be accidental. We already saw a Falcon 9 oxygen tank fail last year. It seemed to be pretty benign & broke apart rather than exploding. The only times they exploded was a range safety detonation in Texas & when the 1st stage fell over after landing.


Someone picked a time when security would be the most relaxed & the high speed cameras weren't rolling. Maybe it was an inside job. They have to inspect for explosive residue.


The sound 5 seconds before the explosion sounded like a someone getting off a tailgate to see what the f*** just happened. The microphone had too much proximity effect for it to be far away.
Posted by Jack Crossfire | Sep 07, 2016 @ 12:29 AM | 1,960 Views
50% off most items. Tried to remember everything will still be available elsewhere, so didn't buy all the stock. The knobs were some of the best things they had & quite a steal. Online shopping is a fortune, in comparison. Wire cutters, perf boards, & 2 channel pots all sold out at higher prices.
Posted by Jack Crossfire | Sep 06, 2016 @ 03:12 AM | 2,358 Views
Since the EQ sounds so much better on the custom amplifier than it did on the HTR-5230, decided the long term should include a bigger front panel with a knob for the bass & enough room for a treble knob. There's enough room to fit 2 more pots by merely making a slightly wider front panel & mounting the pots diagonally. Also, the order from left to right needs to be power switch, LED, EQ, volume. This is the international front panel standard.

The HTR-5230 had 2 25k pots for the EQ & a 100k pot for balance. The 100k pot was specifically for balance & couldn't be reworked as a resistor divider.

The treble is always going to be at full. Sometimes the bass should be at full & sometimes it shouldn't. This was realized by Japanese decades ago, with their famous bass boost knobs. Helas, the age of bass boost is long gone. Steve Jobless didn't include it on the ipods & everyone has since dropped it. Not sure why this is.

A load switch to disable the amplifier until after the CS4227 initializes is on the plan. The speakers also need a way to easily pitch up & down.
Posted by Jack Crossfire | Sep 05, 2016 @ 12:54 AM | 2,294 Views
It's rare for anything to work when transferred to the final assembly. In this case, the sound was still perfect, but thermal management was gone. The 5V regulator was pegged at 93C. It took a major rework to add a heatsink to it. It's adequate for normal apartment use. The regulators & STA540 stay in the 50C range. For 20Hz sine waves at high volume, fuggedaboutit. The 12V regulator instantly jumps to 100C & shuts down.

There were definite compromises for cost. It would have more power with a PC power supply, but need a lot of space. A 19V laptop brick with linear regulator was the most compact. A lot of wires & heatsinks are flapping in the breeze. It's unsuitable for a vehicle.

Adjusting treble is a buster. The probe points for R1, R2, R3, R4 are shown. R1, R2 determine the treble. They're both 40k when the pot is centered. R1 or R2 is 62k when the pot is fully deflected. The resistances can be calculated by applying parallel resistor equations to the Baxandall schematic.

Bass can be adjusted visually, but the bass pots turn in opposite directions. Probe points for bass resistors are R3, R4. The EQ could be broken out to a front panel extension, but it isn't changed often enough.

The 12V regulator is adjusted with R5 & its output is measured at the cap terminals. Voltage must not exceed 16V or the caps will explode.

The output of the DAC is attenuated with R6, R7 before going to the front panel volume control. The...Continue Reading
Posted by Jack Crossfire | Sep 04, 2016 @ 02:52 AM | 3,522 Views
It came together manely as expected. The mane difficulty was getting the STA540 to work. For the STBY pin, the datasheet says MAX V for play is 1.5V, MIN V for standby is 3.5V. In reality, STBY needs to be pulled up for play & grounded for standby. Trap for young players.

The CS4227 needed a substitute microcontroller to initialize it, as expected. Quite a few more registers had to be set in a certain order to initialize it, which weren't sniffed by the oscilloscope. The YM3436 needed a few pins biased, as expected. Traces had to be cut. The mane challenge was both chips needed reset to be low for a certain time after powering up. The YM3436 wouldn't initialize if reset started out high.

The complete DAC took a lot of power. The +25V rail wouldn't initialize when connected to the 10V regulator. The 10V came from a 5V regulator with a 5V virtual ground, but the +25V rail started below 5V. The regulator seemed to detect the +25V rail starting below its virtual ground of 5V & shut down by some kind of SCR latchup. +25V ended up connected to the raw 12V. The 5V virtual ground initialized properly.

The total quiescent current with the power amplifier & DAC was an insane 0.35A. The 2 5V regulators got quite hot. The STA540 needed a large heatsink. The mane problem when playing sound was the DAC needed its ground connected directly to the ground on the STA540. Connecting it anywhere else on either the signal or power ground caused distortion....Continue Reading
Posted by Jack Crossfire | Sep 02, 2016 @ 01:03 PM | 1,705 Views
In the blog's opinion, it was an electrical fire in the avionics package. The 2nd stage wasn't firing its engines. There's no umbilical where the explosion started. The explosion started where the avionics are. It would have been burning for some time before getting into the LOX tank.

The mane effect is redesigning & certifying the avionics package will take a year. There's no PC board manufacturing capability in US. Every revision has to be made in China, which takes months. There won't be any astronaut capability until the next decade. Fortunately, NASA bought Soyuz flights into the next decade. Pad 40 will be abandoned in place. They'll have to wait for pad 39 to be finished.

The money flow will be affected. Of NASA's 2 commercial ventures, the commercial cargo venture was executed as well as can be. It got a few flights off before becoming dominated by failure. As consumer prices rose, the failure rate also rose until the last 2 years weren't adequate to supply the ISS. The commercial astronaut venture was never fully funded at all. In its 7 year history, nothing flew.

H-Rod will continue the 2 commercial ventures, but there won't be another one of the same magnitude. The commercial crew venture will be funded a lot more slowly, to be sure. The SLS won't be replaced by a commercial vehicle where it might have been last week. There won't be any NASA money for the raptor engine. Military contracts will go back to ULA.
Posted by Jack Crossfire | Aug 27, 2016 @ 10:42 PM | 2,051 Views
So after humming along for a few hours, the same LA4461 failed the same way it did 18 years ago. It dead shorted the speaker to the rails, overheated, & made static. Because of the commute, the decision after decades of planning to make something custom out of old MOSFETS, reading comments on the DROK, & a brief dreams of tubes, was to invest in a bog standard STA540 from $parkfun. It would also be the most compact.

The LM324 was replaced by an LF353 on a carrier board. The LM324 appeared in 1972, so judging from the sound of recordings in those days, a bipolar op-amp from those days probably wasn't up to the task.



Reworking the HTR-5230 begins

Analog input proved too noisy. Reviewing the available datasheets for the HTR-5230 revealed the TOSLINK input could be extracted from it for use in another amplifier. The dual TOSLINK inputs were multiplexed into a single input by a simple voltage level. The single input went into the 1988 era YM3436 which converted it to I2S. This was configured by simple mode select pins.

The I2S went into the 1999 era CS4227 which had the DAC. The I2S was routed through the undocumented YSS908 to process the special effects. It could easily be hotwired to bypass the YSS908.

Everything uses 5V at a fairly high current. The CS4227 is configured for SPI. You can see data on the AD1/CDIN line when changing inputs. CDOUT isn't connected. CCLK goes at 100khz & sends 2 bytes when changing inputs. CS is erratic.

The...Continue Reading
Posted by Jack Crossfire | Aug 21, 2016 @ 09:10 PM | 2,679 Views
Built a Baxandall tone control to try to get more treble. That did the job, but with severe distortion. The LM324 wasn't up to the job. The next step is an LF353 on a carrier board. The multiturn pots are quite impossible to center. Given the schematic for a Baxandall, simple resistor calculations give 40k when the pots are centered even though a standalone pot would give 50k. Fortunately, the only useful setting is maximum bass & maximum treble.

This is the only audio circuit the LM324 has had any problems with & the internet approves its use. Anyways, the virtual ground shows a bit of instability typical of the LM7805. Thought the distortion 10 years ago was caused by servos, but clearly it's not a perfect regulator. With the bass set to neutral, the distortion is more bearable than not having any treble. Would say the high end from the 1980's amplifier & Bax is clearer than the HTR-5230, but a true comparison with the HTR-5230 is impossible because it's dead.

Hollens family music is good at reproducing the distortion, because they have the high pitch voice & bassy piano.
Posted by Jack Crossfire | Aug 21, 2016 @ 12:34 AM | 1,565 Views
For the 1st time in 18 years, the IC pair made noise. The circuit was free from defects & did a lot better than the HTR-5230. Standby current was 160mA. They seem to need the full back panel for heat sinking. As expected, the high frequencies were gone because of the lack of a tone control. Being of much older age makes treble enhancement essential. Volume control used the ultra shmick MAX412 with 28Mhz gain bandwidth product to try to retain as much high frequency as possible.

Other than nostalgia, it's rather pointless considering a modern amplifier with 3x the power is $15. The TDA7377 does 2x30W with a lot less parts. The LA4461 does a mere 12W. Quiescent current is the same on both chips.
Posted by Jack Crossfire | Aug 20, 2016 @ 04:57 AM | 1,715 Views
It was disappointing to discover TOSLINK was not decoded by a SOC but a very complicated, shielded board. The key component was the YSS908, an undocumented Yamaha chip which had the DAC & multiplexed all the inputs. The SDA & SCK pins revealed an I2C interface. Mike Harrison could reverse engineer it, but a better waste of time would be to use a more modern digital format than TOSLINK. The only reason for the cable was the amplifier being limited to just that. It's a miracle last year's Macbook still supported TOSLINK because of the number of legacy amplifiers.

For the moment, it's back to ages old RCA cables again. For the tone control, it would make more sense to use a digital input with EQ in a microcontroller than an op-amp. A TOSLINK decoder could be made out of a modern microcontroller, for the true believers.
Posted by Jack Crossfire | Aug 18, 2016 @ 01:19 PM | 1,808 Views
Over the years, the plan varied from reworking the Yamaha's parts into a discrete 2 channel amplifier to nihilistic plans for tubes. In the end, the future was the most economical bog standard IC amplifier. A quick test of the broken DM-01 revealed it probably failed from broken solder joints. 20 years of hindsight would have saved a lot of money, because what was succeeded by 3 amplifiers which failed in their own ways & a lot of heartache would again become the standard.

Unfortunately, the DM-01 electronics were discarded long ago & the speaker driver failed for an unknown reason. Perhaps someone put 12V directly through it. Whoever discarded the electronics strangely left behind the heart of the DM-01: manely the LA4461. The LA4461 is a long discontinued single channel IC with a lot more external components than a modern part, but the nastiest bits of the LA4461 were all preserved on its carrier board. Datasheets 30 years ago were a lot harder to read.

The mane piece not on the carrier board was an oscillation suppression circuit. The test seemed to work fine without the oscillation suppression circuit. The LA4461 produced plenty of loudness from the phone with no additional gain. The only other piece in the discarded section was the tone control. This seemed to be a standard op-amp circuit which combined volume with bass boost. It could be reverse engineered, but the mane requirement in old age is treble boost. The rest was all power supply.

...Continue Reading
Posted by Jack Crossfire | Aug 17, 2016 @ 01:40 PM | 1,449 Views
Behind the nonstop H-Rod worshiping, this was built. Liquid methane would have been 1/3 the size. The 1st, cheapest configuration would be 8.3 million lbs of thrust or slightly more than a Saturn V. The SRB's alone would nearly match a Saturn V. This increase would lift 154,324 lbs to LEO or 1/2 the Saturn V capacity. All the increase in thrust to lift less to orbit is government at it's best. The SLS uses 2 stages instead of 3. The 2nd stage has a lot less power because it uses a 1950's pre-Apollo engine to save money. Recycling shuttle components came with a lot of compromise.

The LH & LOX tanks are the 1st things in 50 years purpose built for a manned lunar mission. The tanks are 35% larger than the tanks on the shuttle.
Posted by Jack Crossfire | Aug 15, 2016 @ 11:24 PM | 1,605 Views
The 1st drive with the speakers was manely successful, owing to experience finally forseeing requirements. The weight was manageable. Low frequencies were quite good. They were just loud enough to overcome traffic & deafening in quiet areas. Either the battery faded or the TDA1517 overheated, because they were a lot more clipped near the end.
Posted by Jack Crossfire | Aug 14, 2016 @ 06:56 PM | 1,283 Views
Because every launch has a few tweeks, it's tempting to collect as much trajectory information as possible in 1 table. Kiwipedia has hardly any trajectory information. JCSAT-16 was a GTO instead of a supersynchronous orbit like last time. The separation velocity was a hair lower to allow the single engine landing. Perhaps this means they found more money can be made by more consistent landings than by giving the customer more speed.


Orbcommmm LEO SUCCESS: 2m25s 6012km/h 74km
1st return to land

JASON-3 POLAR FAIL: 6147km/h 66.5km
Failed landing leg

SES-9 supersynchronous FAIL: 8325km/h 64.6km


CRS-8 LEO SUCCESS: 2m34s 6608km/h 71km
barge landing

JCSAT-14 supersynchronous SUCCESS: 2m41s 8355km/h 66.6km
Payload separated at 36276km/h 207km
1st 3 engine landing

THAICOM 8 supersynchronous SUCCESS: 2m40s 8343km/h 65.6km
3 engine landing, bent struts

Eutelsat/ABS supersynchronous FAIL: 2m39s 8361km/h 65.7km
3 engine landing with longer single engine phase. ran out of fuel

CRS-9 LEO SUCCESS: 2m22s 5688km/h 59.6km
1nd return to land

JCSAT-16 GTO SUCCESS: 2m36s 8156km/h 64km
Payload separated at 35240km/h 208km
single engine landing


Doing the math during today's 8.9 miler, it became clear that the BFR will be 13.5million lbs of thrust or 1.8 more powerful than the Saturn V. If thrust was proportional to the LEO mass, it would translate to 500,000 lbs to LEO. Full reuse is converging on 1/4 of the expendable payload, giving 140,000 lbs to LEO. It's probably enough for a capsule full of 100 people. There would have to be another flight full of fuel & supplies. A permanently orbiting booster would take the MCT to Mars. Fortunately, someone is working on the problem.
Posted by Jack Crossfire | Aug 14, 2016 @ 12:11 AM | 1,527 Views
So Dr. Franklyn got some long needed grinding to add more clearance. It had no problems other than rubber hitting plastic where the manufacturing was off by a few mm. Other than that, Dr. Franklyn has a bit of plastic filings around every moving part.


Finished the poor lion's speaker, finally. Due to some kind of accident, it only has 950uF for the mane power when the datasheet said 2000uF. That might explain why it didn't do the full waveform for 4R speakers, but it also might require 14V to support 4R speakers.

So 2 speakers paired to give 8R to a single channel is what it is for the 1st test.
Posted by Jack Crossfire | Aug 13, 2016 @ 02:04 AM | 1,504 Views
1st automated cam success (1 min 46 sec)


The answer is yes. Automated cams work. They're not completely foolproof, but with enough error protection can do a decent job. The 1st automated cam ended up being LIDAR based. The trick with LIDAR was building dense point clouds out of many passes.

All the basic limitations of XV-11 LIDAR apply. It only detects horizontal motion, not vertical. It only works indoors. It can't handle lots of mirrors & windows. It can't detect anything more than 4m away. It can't handle 2 simultaneous sources of motion. It does better at night than daytime with sunlight coming in. The worst case is the camera pans away from the subject.

The less ideal conditions can be handled by classifying more pixels as outliers, but this makes the camera lag more. The room had a small number of windows which still resulted in a usable amount of lag. It tracked for 45 minutes at night without any failures. As the subject moves farther away, the harder it is to get the camera to track with the amount of filtering required for the windows. It's very limiting to not have vertical tracking.

There's still a plan to try a machine vision approach, with its own set of limitations. A thermal cam might do it, but these are extremely expensive.

When the mobile app billionaires finally get automated cams fast enough & reliable enough for the masses, they're going to be a game changer just like brushless gimbals. GPS quad copters won't do it. Cheaper LIDAR is the key.