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Found 10 results

  1. RF for PF

    Dear All, here is another thing that was for long on my mind: Extend the range of the IR light based one-way communication for controlling the PF receiver without line-of-sight. There are many ways to do this; one would be to install IR repeaters all over the place; this has been realized by others in many different ways. An alternative is to access the PF receiver via radio frequency (RF). This again was done over and over again – my solution is a little minimalistic and simple but works very well. Executive summary (for those not interested in the details of this post) Motivation: Access to PF receivers without line-of-sight, particularly for PF trains. How to add a power/data 3 pin socket to the PF receiver (#8884). How to reversibly plug in a single LINX RXM 433 (or 315 or 418) MHz RF receiver chip into the modified PF receiver and use RF for communication. Result: With RF receiver plugged in, the PF receiver is accessed via RF, with RF receiver removed it works as before with IR control. Benefits: PF operation without line-of-sight Using all three available RF frequencies (315, 418, 433 MHz), 3 x 8 = 28 PF devices are independently controllable. When running newer PF receivers using the 1.2 PF protocol and knowing how operate the address bit in the 1.2 PF bit protocol, 3 x 16 = 48 PF devices are independently controllable. You may want to skip the remaining part of this post ... On to the details Upfront: It works perfectly well, I am very happy. However, I believe Philo’s superb knowledge is needed to explain why. Maybe you can help out, Philo … see further below. My approach builds on stone-old RF receivers from LINX. I bet there are tons of other devices out there, which outperform the LINX chips by far. I simply had these in bulk from China and I knew they behave well, when non-electronics people like me play with RF … The principle is as simple as it gets: The LINX RXM 433 chip constantly listens for a 433 MHz signal, once it finds one in that RF space it pulls its output from ground (= no such signal present) to VCC. A LINX TXM 433 chip does the opposite: It constantly monitors it’s logical input pin to go to VCC and then sends out a 433 MHz signal. This way a simple on-off-keyed (OOK) communication becomes possible. No encoding - no nothing, just OOK. These chips are just that: 433 MHz receivers and transmitters. I have already used them in this LEGO project.. Hacking the PF receiver Here is the part purists will hate though: We need to tap into the LEGO PF receiver electronics to get straight access to the PF receiver’s micro-controller data input line. This line should be directly connected to the IR receiver’s chip data out pin. Steps 1 to 3 Disassembly of the PF receiver as shown on Philo’s pages here. Details in 3), right, suggest to push the PF pins with a small screwdriver out of the socket – this way all 4 stay connected to the wire. It is then easier to get them back in place: Step 4 and 5 4) White arrow indicates the three pins we want to get access to. 5) Bending back the TL/VS/OS-type(?) IR receiver – there are so many of them. The one built into the PF receiver could be an OS 1638 (Philo – help!) – this one has a metal shield and voltage range of 2.7 – 5.5 V which fits nicely. The detail shows the 3 pin socket to be soldered with cut pins and solder applied. Step 6: Soldering a 3 pin socket terminal strip (2,54 mm) as shown here to the soldering side of the printed circuit board. Right: 4.15 V between VCC and GND with fully charged batteries, see volt meter reading. Step 7 and 8 7) Bending the IR receiver back into position. 8) A little drilling is necessary to widen the opening in the translucent plastic part – you may well use more sophisticated tools though. Steps 9 to 11 9) This is how it looks like after drilling (3 mm drill). 10) After cutting/filing the modified PCP goes back into the housing. Before we do that, we need to ply off one side of the yellow cover of the sliding switch, otherwise it will cover the 3 pin socket when in the channel 1 or 2 position. 11) Put the receiver back together. It now still works fine with IR control, nothing has changed so far. But we do have access to the micro controller’s data input as well as a nice power supply of about 4 V. Again, the power scheme on the receiver is shown. IN = logical data in. What makes life rather easy is that all the IR receivers (I know) have an open collector output, pulled up internally to VCC with 10 … 50 kOhm. Which means that you can simply put them “in parallel”. TLC did that in their RC trains #7897 and #7898, which has such detectors mounted on both sides. I looked into the RC electronics built into the casing permanently attached to the base plate, and indeed both IR receivers are hooked up in parallel to the micro controller. So in principle, one can now hook up further IR detectors to the PF receiver. A little test setup confirms that: But that’s is not what I wanted – radio control was the goal. The LINX RXM RF receiver assembled further above works with up to 4.2 V VCC which is a perfect match. And now it comes. As far as I am concerned, we need to invert the output of the RXM chip, which is VCC for a 433 MHz signal present – the IR receiver pulls its output to ground when 38 kHz IR light is present. I tried that: DATA out from the RXM via 1 kOhm resistor into a standard NPN transistor which should result in an inverted open collector output. The pull-up resistor to VCC is not required as there is one in the IR receiver. It works – but not robustly enough. I don’t know why – IR always works, RF “sometimes” not. Which means: Out with it. What works though is: Directly connecting the RXM output to the PF receiver input. IR is then not working anymore, but RF works flawlessly! This is what I wanted to ask Philo: Why on earth is that??? Here is the data sheet: - and here is a sketch of the circuit I tried to use: This is how the PF receiver looks like, when the RF module is plugged in. In this configuration, IR does not work anymore, as mentioned above. Which is (accidentally, to be honest) very nice, as the receiver is not caring about any IR commands - and does not get confused. Upon unplugging the RF module, IR is operational again. Making the "RF receiver" Here is how I got it to work ... This is the "circuit diagram" (it is not, it is just how to solder the wires to the LINX RXM device. There are two chip versions shown: The one on the left (LINX RFM 433 LC-S) reached it's end of life longer ago, the one on the right (LINX RFM 433 LR-S) is the one currently sold. Pin-out is identical, the LR-S type has one additional output (RSSI), which I do not use at all. The LC-S chip is available from China dead-cheap, the newer for example from Mouser and many more suppliers of RF stuff. Step 1 to 3: 1) Tie both ground pads to ground and get the ground wire out. 2) Get VCC, DATA, and Antenna out. The Antenna should be 16.5 cm long. 3) Apply some heat shrink tubing around VCC, GND, and DATA wire. Step 4 and 5: 4) Solder the three wires to the 2,54 mm 3 pin connector in the right order (VCC right marked in white, GND center, DATA left. 5) Covering up with wider heat shrink tube – and done. A little white dot on both the receiver and the RF “module” helps to get the right connection. Both devices suffer from no damage at all though when hooked up in the wrong way (extensively tested). On the RF transmitting side the PF IR remote control (#8885 or #8879), an IR receiver chip and a RF transmitter is needed. For simplicity I used a LINX 433 TX LC/LR transmitter in combination with a TSOP 34838 IR receiver. Any 1738 or the like would do as well. In fact the IR RF transceiver referenced already above works fine. So what do we do with all this? First, communication without line-of-sight works very well – a video should be available soon demonstrating that (a train behind a bookshelf or in a tunnel). Second, the LINX chips are rather small and more importantly very robust in operation. The power consumption is reasonable and is readily available from the modified PF receiver. Third: The LINX chips also come as 315 MHz and 418 MHz versions. Which means that 3 x 8 = 24 PF channels are readily available. As the PF receivers don’t “see” the IR light anymore when the RF chip is plugged in, there is no IR trouble at the receiver side. On the transmitting side one has to make sure that the PF remotes do only shine their IR light onto the corresponding RF transmitter. Fourth - and most importantly for me: I got hold of an NXT IRLink sensor from HiTechnic. The IRLink natively “speaks” the RCX message protocol, the PF protocol, and the RC train protocol. It is some kind of C3PO – uniting the LEGO IR world. With the exception of Manas, I believe. I wrote a little NXT-G program that listens for RCX messages (in RF space that is), captures the ones that are of interest, interprets the data content of these messages and sends out PF or RC train commands into RF space. Any RC or PF controlled train equipped with the RF receiver will do what it was told. I am running 8 PF trains and 1 RC train using this scheme. And this is up next: Controlling PF trains with NXT + HiTechnic IRLink via RF communication. Requires certainly a little time though ... Thanks for reading. Regards, Thorsten
  2. Hello all, I'm trying to find a way to create a power/data coupling between train cars that can be connected/disconnected like the car coupling magnets. Has anyone done anything like this? Background: This is so that I can supply power and control to LED lights (and maybe other devices) in the cars being pulled behind the engine, which will provide the power and control unit (Arduino based MCU) I've tried using a micro USB magnetic connector, but they are too bulky and don't flex easily enough for this. I'd love to find out if anyone has engineered anything similar. Thanks in advance! Arlo
  3. Hello fellow train builders, I would like to share my most recent project theme; Lego Trains & Internet of Things. Basically, I make connected trains and train related stuff. My aim is not to be 100% realistic or copy existing real world trains. My goal is to bring Lego into the IoT movement, learn many great things along the way, and eventually help the next generations to get interested and pick up the necessary skills for a better world through technology. Let's call this STEM through Play.(STEM=science, technology, engineering, and mathematics. Sounds like a mouthful, huh? but that's what I want anyway ) Without further ado, here's what I have built so far; Automated Lego Railroad Crossing Lego Train Voice Controlled Lights via Amazon Echo Lego Train Controller App Please bear in mind that this project is new and under development. I welcome any sort of feedback and questions I will also update this thread but if you'd like to keep up, here's my website which aggregates all the social channels related to this project: Legongineer
  4. IMG_0560 by JJ2Sam, on Flickr Hello, Here is my new MOC I named "No limits", It features Traxxas Titan 380 motor Tenergo 5000Mah 7.2V battery HobbyWing Quicrun ESC Futaba Standard Servo motor Custom CNC milled aluminum parts by Brick Machine Shope 3D printed 4bevel gear differential by kind Efferman :) FlySky remote + receiver When I first build this it had full independent suspension but it was melting the CVjoints and UJ's I was using so I settled with a pendular rear suspension for rigidity and a single spring independent suspension for the front. Overall the suspension works well on pavement as well as on loose dirt or gravel terrain. Effermans custom differential works very well and has never ground gears even after my brutal driving and the high RPM's it is spinning at. IMG_0557 by JJ2Sam, on Flickr IMG_0555 by JJ2Sam, on Flickr The single spring front suspension really helps the performance because it basically allows one wheel to go up and the other down in the same motion much like a bogie but still allows up and down movement. One thing I am not happy about it is the HORRIBLE geometry since the top beams are monger then the bottom ones making it have a negative camber angle. The pendular rear suspension was the only choice since I dont have Effermans custom CV joint parts that would allow full independent suspension with drive. IMG_0558 by JJ2Sam, on Flickr IMG_0559 by JJ2Sam, on Flickr I mounted the ESC and receiver up high to allow air flow to cool the parts and have easy access to them. The battery was mounted very low with only 2 plates protecting it from the ground kept the SOG really low so I could do full-throttle 90 degree turns without flipping over. Overall it performs VERY well and has not flipped over ever and has broken the Lego speed record by doing 32kph IMG_0586 by JJ2Sam, on Flickr Hope you enjoy and please leave a vote on the poll on how you like the use of custom electronic parts.
  5. brebo Hi, I have launched a KickStarter (crowdfunding) campaign for a simple, low cost and intuitive system to invent and recycle electronics using Lego. Have a look [removed url] Let me know what you think. Thanks!
  6. Fragment of printed circuit board with microchip and SMD capacitor in a scale of 20:1. Microchip by vir-a-cocha, on Flickr
  7. Another AFOL here!

    Hi everyone! Just saw this "introduce yourself topic" so here I am. I'm lurking around for a few months now and so now and then I post my own creations. I discovered that this is a really cool forum with loads of people who are even more enthousiastic about Lego than I am. For me, it all started in 1985 when I got the 7727 train for my birthday. I had never been so happy! Since then I got some more Lego sets and when I grew older I switched to Technic and bought the classic 8868 and the 8880 for myself. Now I combine Lego with electronics: I'm building all kinds of robots and recently I've built a huge automated train track (see my posts). I don't use the NXT platform; it's quite expensive and I like to develop all the electronics myself. Since a few months I'm building a robot that's going to fetch me a beer from the fridge but there are some obstacles to take. I'll open a topic about that soon. Cheers and let's build cool things!
  8. Hello! My Rescue Helicopter (9396) is about to be delivered ( ) and I have this idea to put enormous amount of LEDs in it. I have a plan to use Arduino to program proper blinking sequence. I was thinking about mounting also 2 M-motors to motorize rotor and functions. I would love to control them via Arduino but I do not have an idea how to connect motors in a proper way. Has anyone ever done it? Thanks in advance for any tips!
  9. Since this is my first post I'll start by saying I've been a life-long fan of lego technic. I'm 29, and I recently got back into the hobby and I'm building a 16 unimog-wheel scale mobile construction crane with at least a 4, and probably 5 section telescopic boom (but it will only go straight up and down. A boom that large made of lego can't work in cantilever. . . at least not work well. Anyway, I have I think 22 m motors from various sets, and I've started testing the motors. Turns out I got a bad motor. I opened it up and the problem is an internal short in the capacitor. If I squeeze it or apply any pressure to it it shorts and the motor stops spinning (and the LED on the battery pack turns off indicating high-current draw protection). I'm handy with a soldering iron and I have small spare capacitors laying around, so I thought about replacing it. I also thought about trying to get a replacement from Lego (either through the internet or at a store). I was curious as to the RMA process through lego. Secondly, I thought about not replacing the capacitor at all, and just taking it out of the circuit. This made me wonder if this would give me IR V2 comparability if I did this to all of my m motors. I understand the importance of a capacitor for noise reduction, which doesn't seem important here since we're using infrared and not RF. I read this post on TechnicBricks a while ago: "The raw motor currently used in the LPF Medium motor internally contains a relatively large capacitor (1 uF) across each of the 3 motor coils. This is done by the motor manufacturer for noise reduction. We knew that this would be an issue with the new CMOS motor driver (DRV8833). Since it can source a very high inrush current the over current protection will kick in sooner (typically after 2,25 us with a current exceeding 3,3 A). At start up the motor driver will first charge the input capacitance. With 2 or more LPF Medium motors at the same output this can trigger the over current protection. It will repeatedly try to start the motors and you will only hear a singing noise. For many reasons we have been searching for a higher quality solution for the LPF Medium motor and we now have an approved new raw motor. It has better quality commutation and only 1nF across the terminal. An updated LPF Medium motor will be released during 2013." All of my M motors are definitely not the new versions, and I'm not sure I'll ever buy any more M motors (because I have enough) and the L motor is about to be purchasable by itself. I guess my question is regarding the above quote is are there 3 additional capacitors inside the motor itself? The capacitor that I can see when I remove the shroud is definitely in-line with the main power wires. It does not cross the poles. If I remove that capacitor will it negatively affect performance, and will it give me IF V2 compatibility? While I'm at it, here's a picture of my build station. And more random pictures of my build so far. Really just prototyping, although the wheel carrier design is finalized so I went ahead and built all 16 of them.!i=2374027084&k=HnHn3Pm