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Archive for March, 2021
Posted by Jack Crossfire | Mar 28, 2021 @ 07:48 PM | 8,590 Views
So the right motor seized up a few times. Upon disassembly, it was scorching hot. The leading theory is the warmer weather is softening the PLA components, throwing alignment off. Motor mounts may have to be printed out of PETG. The wheel was definitely deformed. A metal plate outside the current PLA one might dissipate heat.

The gaskets were chewed up, probably from the wheels slipping out of their bearings & being shoved back in.

There is a condition where the radio frequency hopping permanently stays out of sync. It gets 1 packet every second. That could happen if the same frequency happens twice in the pattern, which it doesn't. It could just get crosstalk from another frequency. Another bit in the packet storing what slot of the pattern it's on might fix it.

There are still rare times when the radio disconnects & it falls back on a motor timeout.
Posted by Jack Crossfire | Mar 27, 2021 @ 08:15 PM | 9,642 Views
Bench testing was ugly, with much worse results than the unamplified radio. It seemed to be saturating the receiver. Moving it farther away or covering it improved reception. Hot glued the bodge wires down instead of making a new board. Buttoned it up & it worked much better in the field. It managed to fend off the phone tower & range was no longer a problem. There were still dropped packets near the phone tower but not enough to kill it.

The impedance matching is obviously horrendous. Having the receiver right next to the ground is horrendous. The lion kingdom was just hoping for enough improvement to do the job. The battery has to be charged after every drive now. It took 30 minutes to hit constant voltage on the inductive charger. Something would have to be rigged out of a multimeter to get the number of coulombs.

The big question is exactly how much power it's radiating, compared to a Spektrum or a DJI. It spreads the 500mW across 100kbits. The Spektrums concentrate 7mW in a very narrow bandwidth so they have long range. The DJI video transmitter radiates 1W across a 20Mhz band of frequencies, so it has shorter range. No-one knows what the DJI uses for remote control. It may be the same as the Spektrum.
Posted by Jack Crossfire | Mar 27, 2021 @ 12:02 AM | 10,941 Views
The upgraded board was a bodgeorama, but it was the lion kingdom's 1st home made transmitter above 5mW.

The trick with the RFX1010 is the antenna input is shorted to ground at DC. It needs a 33pF blocking capacitor. Then, when the transmit enable pin is on, it burns over 150mA with no input. When the transmit enable pin is off, it burns nothing. This pin needs to be actively turned off when not transmitting. Receive enable & mode have to be grounded to get it to completely shut down. The control pins are floating. Mercifully, the switching time is only 1us.

Then of course, the high power requirement of the amplifier caused problems. The ADC became unreliable when the amplifier ran. Making it use the dedicated RC oscillator got it to work for some reason. The LP2989 voltage regulator got stuck on 2.5V until it got a 100uF input cap.

When it finally worked, it only burned 50mA for the full 500mW. The duty cycle was low enough to use full power without killing the battery. Frequency shift keying in the single channel mode & the 9 discrete channels used in the frequency hopping mode are clearly visible on the spectrograms.

The gold standard in the commercial world is the DJI Mavic, which only transmits 400mW. The top end Spektrums only transmit 7mW at 2.4Ghz. They obviously rely on directionality.

The mane problem with getting any more power is the small form factor, small battery, & not being able to use a directional antenna.
Posted by Jack Crossfire | Mar 21, 2021 @ 09:23 PM | 11,375 Views
The mane problem with these controllers is lion paws being asymmetric, but a method has evolved to work around the asymmetry. It's just not as comfortable in the right paw as the left paw.

The direct drive motors have 400 miles on them. Since the loose motor


they've been manetenance free for 218 miles. The mane problem is the wheels occasionally slipping out of the motor bearings. They can be shoved back in, in the field.

The 4Ah battery of 12 years ago is now down to 3483mAh capacity. Its nominal consumption of 250mAh/mile now gives it 13 mile range.

Anyways, the lion kingdom took note of the go go bird controller. Like the boosted board controller, there's a common theme of a binary switch for unlocking & a 2 axis joypad for throttle & steering. The center of the joypad is "hover". The question naturally arises of why these guys don't have separate throttle & steering sticks like it used to be done. The leading theory is it's cheaper to have a single proportional control + a binary switch than 2 proportional controls. It has nothing to do with ergonomics.

The lion kingdom also tried the TV controller orientation of the go go bird controller & was disappointed. Those aren't intended to be held by sweaty paws for hours.

French amazon had detailed photos of the components while American amazon had gender neutral photos of child models playing with it. After 40 years of seeing this difference in marketing styles, there's no evidence an economic system based on knowing how things work is better than an economic system based on social justice.
Posted by Jack Crossfire | Mar 16, 2021 @ 02:29 AM | 10,603 Views
9 mile timelapse (4 min 24 sec)

No more stable than the lunchbox. Burned 321mAh/mile. Had to reduce the steering feedback.

The gimbal had a strange tendency to move off angle when the controller was turned off, then move again when the controller was turned on. There's nothing in the source code about turning off the motor when the controller is off & the motor definitely doesn't turn off. It may have been operator error.

That stepper motor burns a lot of power & requires a lot of space for gear reduction & electronicals. There's a definite case for moving to a 360 servo just to increase the driving distance & free up space. Lions see no advantage to the stepper motor, now that it's gear reduced. Either way though, 20 miles is the goal for the camera & it would still require a 2nd battery with a servo.

It gets bashed around so much, a servo would require another plastic bearing, but it would have enough torque for plastic bearings to not be as problematic.
Posted by Jack Crossfire | Mar 15, 2021 @ 02:02 AM | 11,666 Views
So far, lions have only designed in unamplified radios of 5mW on their own boards. Extended use of these radios has proven disastrous. Their range is only 15ft. The mane problem is near phone towers. The GSM bands overlap the 900Mhz ISM band so they die completely. Frequency hopping did nothing to improve it.

5mW was good enough for 13 years of indoor flying & stationary weather stations. When they're well above ground & using well aimed directional antennas, they can go 500ft. Thus, it was hoped they would be enough for outdoor driving.

There are only 2 low cost chip amplifiers on the digi key: the 1W SE2435 & the .5W RFX1010. The lion kingdom went with the .5W because it's much smaller to hook up. As usual, it's a 2 week snail mail time. The limitation on power is the battery life. Some reduction of the output power well below .5W will be required to manage the battery life.

The XBee Pro 900 made 50mW & never had any dropouts when driving. It was worthless in the longer ranges required for flying, but it was flawless for driving. It was just too big to fit in the modern controller. It burned 210mA all out. The duty cycle got it down to 100mA.

The unamplified transmitter burns 10mA to get 5mW, with some more for its LED. It has a 50mA budget if it is recharged after every drive, which could limit it to 25mW. Packet size & baud rate can buy some power before the whole thing needs to be reprinted for a larger battery.
Posted by Jack Crossfire | Mar 13, 2021 @ 04:04 AM | 9,851 Views
After a white knuckle drive at night, the container was deemed finalized enough & the decision was made to finally put in the headlights. They incorporated many improvements which came to mind over the years. Wires were put on the inside. Paw written icons replaced 3D printed icons. A new combination of hot glue & a zip tie was conceived. The mane problem with LED farsteners is the LED shapes vary & they have to be as exposed as possible. Their mane function is warding off traffic rather than lighting the road. Helas, the grey PLA is always going to be less visible than white coroplastic. There is a bag of LED tape which could be temporarily farstened for special occasions.

Because of the difficulty farstening the container corners, there is a desire to move the headlights halfway down.
Posted by Jack Crossfire | Mar 09, 2021 @ 05:54 PM | 13,020 Views
Expected it to RUD, but it held together. It was noisier than coroplastic. It wasn't noticeably heavier. It burned 250mAh/mile. After all the effort designing the isogrid container, began pondering a more tactical color scheme. For the last 30 years, the tactical color scheme has been desert camouflage. It could be printed with tan PLA.
Posted by Jack Crossfire | Mar 07, 2021 @ 09:54 PM | 11,729 Views
It took a full day just to swap the container, as expected. Headlights still have to be installed. There is a debate whether the speed fluctuations are from radio interference, tachometer glitches, or PID oscillation. Tried reducing the throttle to just 1 speed instead of 3, but it still had speed fluctuations. There is a desire to improve the radio error detection by XORing the packet with a key, but so far, there's no evidence of the radio causing speed fluctiations.

Finally put in a better buck converter to replace the crummy 3A Turnigies which are taking over the world.
Posted by Jack Crossfire | Mar 06, 2021 @ 02:30 AM | 8,390 Views
The 1st drive in the city was awful. The radio has had growing pains, as it has been driven farther. It 1st started dropping out when near a phone tower. In the city, phone towers are a lot more common & the radio was all over the place. Never had this problem with the higher power 900Mhz radios. The lower power 900Mhz radio is no match for phone towers. It's surprising how frequency hopping made no difference. There's not enough room in the remote for an XBee.

There are other single chip radios besides the MRF49XA/SI4421. Antenna placement is not the best. They're bundled with a lot of other wires. Another idea is creating a phone app to make the spectrum analyzer portable enough to find out what is jamming it.

In the apartment, the spectrum analyzer shows it neatly divided into 9 channels as programmed. It's hard to believe anything could jam out all 9 channels. There are still a few blips when it's off.

Lions aren't very enthused about creating another phone app for test & measurement. Goog has clamped down more & more over the years on what apps are allowed to do. Out of a growing desire to have more control than Goog allows, there's a growing desire to fabricate a portable confuser out of a single board confuser, bare LCD panel, bare keyboard & touchpad. The single board confuser would be standalone inside a brick. The keyboard & monitor would be in a separate clamshell, either connected by wireless to the confuser or some kind of dock, but it wouldn't be transported in 1 piece like a laptop. It would be a 2 piece laptop.
Posted by Jack Crossfire | Mar 05, 2021 @ 02:27 AM | 7,623 Views
The motors still tend to pop out of their bearings & get stuck. Fortunately, they can still be forced back in, in the field. The encoders are now far enough inside to manage to stay in place. They still need shaft collars.

Anyways, the lion kingdom was left with a pile of solar cells after a failed attempt to make a car battery sustainer. Enough solar cells to do the job would end up costing more than a new battery. They make 1W in direct sunlight & 12mW in shade. Slightly more power could be extracted by matching the load to the cells. They were each rated for 60mA at 5V. https://www.amazon.com/gp/product/B089793L93

For a solar powered car battery sustainer to really work, it would have to be parked in direct sunlight all day. There isn't any electrified car port for thousandaires. It's hard to believe there was ever a time when houses were only 5x an average annual income, but lions still remember. It's been 20 years since the multiple became 10x & it's never gone down. The average electrified garage is now 15x the average salary. Lions believe the multiple will keep rising as long as the global workforce continues expanding faster than demand for labor.

There isn't any obvious, practical use for the solar cells. Besides the car battery charger, they would just power toys. At running speed, they would add 3/4 miles of range to a robot with a 4Ah battery. At walking speed, they would add 1.25 miles. Range extension would increase as speed decreased, until a robot could crawl as long as the sun was up.

Ironically, as green tech took off 10 years ago & then electric cars took off 5 years ago, interest in solar powered toys has gone away. BEAM robots, photopoppers, photovores used to be everywhere. Not sure if the solar hobby enthusiasm as been replaced with green tech day jobs or of the current generation sees solar projects as something government initiates rather than individuals in a garage.
Posted by Jack Crossfire | Feb 28, 2021 @ 07:42 PM | 9,160 Views
A 19 mile drive brings out the defects. The bumpers fractured between the laminations. So flexing can't be perpendicular to the laminations. One does not simply rotate the laminations. Thus began the 1st attempt to adhere TPU. E6000 was hopeless. There was hope for CA with a tongue & groove.

It was the 1st time anything went that far on a single battery. The power usage was 216mAh/mile.