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Kalkhoff durban G9 Ebike - Display mod

2019-08-25T00:00:00+02:00

E-bike buying decision

Last year in October I bought a Kalkhoff durban G9. It is a 28" bike with a mix between a load and a touring bicycle.

It wasn't my first choice but for my usage it is enough and fulfilled all requirements.

I wanted to have a normal size bicycle with a lot of storage space for groceries. Also, the range does not have to be super huge with about 30-40km but I shall be extendable if need more at a later time for some tours or the battery capacity drops on aging.

Therefor I found the Tern GSD and the Kalkhoff durban G9 pretty appealing. The GSD costed about 4000€ and the Durban 1200€

First I wanted to have a Tern GSD, since it would more fit to me from point of driving and loadable storage. Also, the lower mass centre and the fact that I would not have to steer against the front rack are the real benefits.

However one big drawback would be the price. I could have bought nearly 3.5 times the Durban G9 for the same price as one GSD.

Another con was that this is a Bosch bike. Bosch Ebikes have for each battery one CanOpen controller inside, which results in the fact that only Bosch batteries can be used. If you would connect a third party battery the motor drive would not support you even though it gets power.

Also, I got the information from a former working college that self replacing the 18650 cells is on some bosh batteries nearly impossible, since they lose the configuration if power gets lost and therefore do no longer work with the closed source CanOpen bus protocol of bosch. So instead of replacing just the 40 cells for routhly 5€ each (in case of good LG cells with 3500mAh) and 200€ in total, you would have to buy the 700€ official Bosch battery.

So I boughth the Kalkhoff Durban G9 since it is much cheaper and the storage room would be enought for me at the current possion. I would however change to the Tern GSD if I would need a bigger storage room or need Kid seats. Then I could sell my Kalkhoff and buy a maybe a used GSD much cheaper than the 4000€.

Kalkhoff durban G9

The Kalkhoff has a rear hub motor SWX02 36V 250W from the chinese company Bafang.

The con I could not lay aside was the fact that this bike system is missing the display for battery values and choosing the support levels. With the official system only 3 steps of support are possible: 0%, 70% and 100% This support levels are choosable via a button on the Battery. This is not even close to comfortable while riding.

Also the battery indicator leds are hard read, since the frame pipe is blocking the view and they are not that bright in sunlight. The angle of the leds are directed more towards the rear crack and not towards the driver.

This issue I wanted to address and disassembled the controller and battery of the durban and did take a closer look.

On the bottom connector plate there exists a bafang typical port for debugging and configuring. This port is the same interface as the Bafang Displays are using to send over a serial bus the support level. After some research I found the pinout and connected my logic level analyser and I saw the protocol of the "display", which in this case coming from the controller within the battery housing.

Therefor I ordered a display from aliexpress which should replace the "display" within the battery. There are several display options available. In order to save space on the handlebars I've chosen the "500C".

For connecting the 500C the 2 serial wires have to be disconnected from the battery controller and only the new 500c is connected to the debug port of the motor controller at the bottom.

There was one problem remaining. The battery is including a display which auto turns off in case it could not communicate with the controller or no moving was detected.

So after 10 min the battery turns off and the motor support is gone.

To solve this issue the Rx cable for the battery has to stay plugged in. With this "hack" the battery reads the feedback of the motor controller but can not transmit its own commands. The Rx cable you can see in the pics below with a XXX isolation.

With this configuration you can choose the support level and limit by the 500c (yes also the speed limit :))

With this the range of the battery can be optimiced so turn off support on easy tracks and add additional support for steep hills if fully loaded. I really wonder why Kalkhoff did no add this kind of display from the start since this display costs about 50€. The only reason I could think of is to have a con or attractive selling points for more expensive bosch ebikes.

quadrocopter

2019-06-20T00:00:00+02:00

Infected by the other members of the Toolbox e.V, especially Thomas I started to search for parts for a quad copter which could be used to race and do some freestyle moves.

Since for me also the assembly is new and I had the feeling that this quad will also be likely to be damaged I wanted to build it with separate components. Also its more fun that way.

Since I did not want to have a huge quad I wanted to hit the 250g Law limit for the assembly. In such a case I would not even be forces to add a burn resistant name tag to the quad, which I would anyway recommend if it could be lost.

After some search i found the Diatone quad frame GT M3 pretty appealing since they have a aluminum cage for the PCB stack and a 3mm carbon plate which is robust enough for a beginner.

The following motors where selected by taking the recommendations of the frame into account: motorsize 1408 motorr 4000KV

The motor size of brush less motors for quad copters are regularly indicated by a 4-digit number The first two digits represent the stator width or diameter while the second ones represent the hight. The values types are in mm

In general the motor size have quite a influence of the flight characteristics. A taller motor most likely result in more power at the upper Throttle/RPM and a wider motor would result in a higher torque at low throttle.

Since I wanted to use motors with a actual data sheet or at least a test measurement how much thrust and amps would be drawn with certain types of propeller I did take a look at the T-Motor F20II F20 II 1408 3750KV

The where the ones which had a lot of thrust with 532g when they are mounted with 3040 propeller types. The goal of the quad would be to be below 250g so the thrust to weight ratio would be 1:8 for a quad copter.

At this point the Motors and Frame where clear. The next step was to choose a propeller type. For this I selected the three bladed one with close to the 3040 size. The only ones which are quite near to this are the Geprc 3042 The Number of the Propellers are also representing the size nearly as the motor identification number. The first two digits are the diameter in inch and the second two ones are representing the pitch of the propeller.

The Pitch is sometimes misunderstood. There are 2 value types of the propeller blade. The actual meaning of it is the forward movement of he propeller if it's rotating 360 degrees. This value is calculated in inch. So if the upper propeller would be measured this schema the 3042 would represent the diameter as 3 inch and the propeller is moving 4.2 inches forward.

However there exists also the measurement of the angular pitch. This value is common for props which have a non constant angle in order to compare them more easily. The conversion from one to the other is pretty simple and can be found the in formula below.

$$ p_{inches} = tan\left( p_{angle} * d * \frac{m_{point}}{100} * \pi\right) $$

$$ p_{angle} = atan\left( \frac{p_{inches}}{d * \frac{m_{point}}{100} } * \pi\right) $$

You can imagine the higher the pitch is the more air is moved and the more thrust it should generate with the same rpm. Side effect of the higher pitch is a higher amp drawn thought. So you have to be carefully which props you putting on the motor otherwise you could overload the motor and they could burn down or the ESC can not handle that much amps.

In my case they are measured in degree so the forward pitch angle of $42°$ would result in a pitch blade of 5.09 inches.

Now we have the motors and propeller selection finished and estimate the amp drawn through the ESC. In my case this is 19.8A per motor or 312.64W. The values of the ESC are also declared typical for each motor. Also the ESC has to work together with the flight controller. Since beta flight already announced that an F3 chip is getting short on the flash I wanted a F4 board. The f7 boards would also work but I did not see the benefit compared to the nearly double cost of a FC. In the end I selected an HGLRC 20x20mm Micro F4 Flight Controller with an 28A Blhel_S BB2 2-4S 4 in 1 ESC

Last but essential components are the video transmitter equipment. There are 2 aspect ratio available 4:3 and 16:9. The choice is just based on preferences since you can also change the lens on the micro cameras and with it the field of view.

I personally like 16:9 since its a more natural view for the eye. Therefor I selected a runcam Sparrow WDR 700TVL As you can image the video is not even close to hd or even hd ready. The video is transmitted analog like the old analog satellite tv with round about 576i@25fps for PAL and 480i@29.97fps for NTSC. This is the case since the video shall be with minimal to no delay transmitted, which is not typical for digital video signals. Therefore these quads are using typical analog video.

For sending the captured video signal I chose a TBS Unify Pro HV Race FPV Video Sender SMA - Team Blacksheep since this does less interference on other channels which Is required if you flying together with your friends. With the china VTX there is a high chance that they have interference if he quad gets powered on.

Lastly I also added a beeper and LED's since otherwise it might be hard to find after a crash in high grass.

part list:

New Webpage

2019-05-22T00:00:00+02:00

Last week I was researching for a better way to generate my webpage. Before I was using wordpress and dozends of plugins to get a website running like I would like it Then my server got corrupted and I had to resetup the website.

This was realy crule and I did not want to deal with the plugin crap again. Also, wordpress was so called 'klickibunti' and I could not write content from my good old vim. :'(

This introduces a to high burden to acually write some blog, since it's not that convinient to write or save a intermediate step and continue again later. Also, if something is not working you have at least the git history to step back and try again. Try this with wordpress plugins.

So overall i have still lot of things to script/implement and add but the main sceleton is now in place.

The HTML is now generated by markdown and translated with pelican into acual html and some minimal javascript.

keyboard with track point

2018-09-20T00:00:00+02:00

I am a software programmer so the main part of the workday I am typing on my keyboard. At work unfortunately the only provide the cheapest HP keyboard you could image. It is a nightmare. After 3 months typing on these I bought me an keyboard myself.

Since I am used to a track point from my x230 notebook I searched for a keyboard which had also a track point for the desktop.

Sadly these kind of keyboards are rare. Since I where a student at this time I ordered me an IBM keyboard. The feeling was nice and I like the track point feature of it. However after 1 year of using this keyboard I broke it at multiple keys. These keys stopped working and the overall feeling was not the same like a new keyboard. This is a cause of the membrane keyboard type. They age quite fast if used extensively. Also the pressure point of the activation changes.

Therefore I searched for an alternative with mechanical switches. They shall last much longer and in case they are broken I could exchange them by soldering new one in.

Therefore I ordered the CM Storm Rapid-I with red key switches. The red cherry switches where linear and do not have a feedback bump. The overall feeling of these keys where nice but after a time I disliked the missing feedback. Also I missed a track point on these keyboard.

Therefore I started a project to integrate a tracepoint into the keyboard, which was not available any where else except the old IBM keyboard which only had an English key layout.

I disassembled the keyboard and did take a look at the PCB. On close look between the keys g and h the PCB only had a ground plane but not real signal traces going around. Therefore I thought of drilling through the PCB and place a long stem with a track point underneath. I disassembled an old keyboard from an T40 and recycled the track point from it. The tack point itself is just a small PCB with a cross shaped cutout and some glued strain gauge in the 4 directions. The secondary PCB is just a fast ADC and a 3 button input converter to a PS2 interface.

Therefore I just had to connect some additional mechanical switches to the secondary PCB and connect it to a pc. Unfortunately the PC's nowadays do not have a PS2 so common any more therefore I wanted a PS2 to USB converter. After short research I found the Teensy2.0 which was capable to emulate a USB device and also is capable to run TMK software which is capable of PS2 reading.

The first test assembling I tried the whole system and it worked like a charm.

Now I got the best of both worlds a track point and also a full mechanical keyboard. The last thing missing was the feedback. So I resolved my wrong order by soldering brown Gatheron which are close to the Cherry brown.

I took it a work and I was happy with it. Unfortunately my office partner not :D So I tried to silence the hell out of my keyboard. I ordered zeal silencer clips and added 2 O-rings. Also I replaced the keycaps with PBT which are much harder plastic and do not wear out or get shiny like the ABS ones. Also I replaced the keyboard case with an aluminum CNC case. This mad the keyboard much heavier which dampened the noise from the desk, removed any vibrations. Also from esthetic's point of view the keyboard looked and felt much sturdier and from high quality.

To round up the feeling I added some lube to each switch and tada the sound and feeling of the keyboard was a dream. Since I have now 2 USB devices in on (Teensy and the original CM Strom) I replaced the USB cable with a own 8 pol cable with two USB plugs and a textile sleeve to get a awesome optic.

3d printer

2018-05-20T00:00:00+02:00

Since this month I own now one small 3d printer. It's a "ender 2" with a build volume of 165x165x200mm. For my purposes this is more than enough, since I always could print larger parts with the Toolbox e.V. printers since I am member there.

The printer was pretty easy to assemble and took just about 2 hours of carefully reading the manual and assembling the parts.

Out of the box the printer was printing prefect. But since I did know that the printer from Creality have disables safety features I installed the latest firmware from the Marlin github repository.

There I changed the config parameters to my need and enabled the following options to lower the risk of fire caused by a printer failure.

#define THERMAL_PROTECTION_HOTENDS // Enable thermal protection for all extruders
#define THERMAL_PROTECTION_BED // Enable thermal protection for the heated bed

With this option enabled I printed a benchy, which came out perfectly. A benchy is a small boot which you can see in the lower picture. It has some structural parts which are though to print.

After some time I did research for some upgrades since some parts where annoying over time.

the noise level

The original board had some motor step drivers which where not capable of micro stepping. Also, they were no exchangeable mounts to replace the current ones with new stepper drivers. The original board had only a AVR atmega1284p and not the big brother the AVR amega2560. This limits you to not enable all features on it.

Therefore, I replaced the complete board with one which had these options. I found the rumba board and choose the TMC2100 since they are capable of micro steps. This made the printer barely noticeable and only he belts where still doing a slight noise.

The second upgrade I did is to replace the hotend with the e3d v6 and added a part cooler from both sides and added a Probe to get a repeatable and reliable printer.

The last update I did was to replace the printing surface. After some time and several prints the ice effect print surface was damaged and a small hole was ripped in the middle. The main reason for this was that the original ice surface had a strong grip on the printed part. Even if the part is cooled down, the 3d printed part was barely removable. A fast wear out was also cased by the slicer. I always printed on the same spot in the middle of the bed. This of course let the bed surface wear out much faster at this place.

For a replacement I wanted to have a similar bed like the Prusa i3S has with the removable spring steel layer which lets you remove the printed part without any tool. This should also extend the life of the printing surfaces since it does not get any stress or scratches. There are only 2 option available buildtack for 60€ and whambam for 30€. Since I did not want to spend that much on the print surface alone, I've chosen the flexible build system from Wham Bam.