Bartosz

Oh! Hope I won't have to resort to this! And not because I'm purist, I'd fear I break it and probably my reassembly would be awful ;D

Hello, While bricklinking some parts I've bought my first switching tracks - used - so I can't compare with new ones. I've got a feeling it's fairly hard to switch (using that yellow part). Sometimes I fear it could break. Is it because the parts are not new, even if visually they look ok? Or is it because they just weren't used for a while? Can something be done about it? What's inside of them anyway - springs, metal parts, could it corrode?

But Brickset lists the current, 7895, with RRP of 19.99€, so the same.

Time for small report! So, after hooking the voltage regulator and 2xAA batteries, the IR receiver would start normally (green led on), but then after sending a signal for motors, the motor wheels barely moved and IR receiver restarted itself. Now, this is a failure, but it's not something unexpected. Probably the current needed for motor to start (haven't measured it) was just too much for regulator, and it did what spec says it was supposed to do - drop the voltage to some level that was probably unacceptable for IR receiver. I was expecting it to happen on stalling - it wouldn't be that bad, because after such stall it would be able to run it again, but I didn't anticipate it happening while starting :) Time to get back to plan B, and use the 9V battery...If only I had accounted for plan B and ordered 9V batteries as well! But I did not :D

I've recently started doing this. But I believe one needs to have real interest in this to spend time assembling parts, figuring out what to build - it's rather time consuming, and I don't see someone with no interest in LEGO (but kids interested in it) trying to do this. On top of that, I came out rather disappointed that I wasn't able to optimize the prices in a way that bricklinked stuff (smaller sets) would come out cheaper than off the shelf sets (larger than what I've assembled). Fun fact about doing this "for kids". Somehow my kids were more interested in sorting bricks with me (of course they fought a bit over it), checking whether order is correct, washing them, than actual building :D

Right, but I was talking about step-up (boosting) regulator such as: https://www.pololu.com/product/2564 There you see that for Vin 2.4V, at 450mA output current, there is 80% efficiency. There are no more measures after that, but they also mention: "If the input current exceeds the switch current limit (typically somewhere between 1.2 and 1.5 A), the output voltage will begin to drop". So yeah - that's what probably been puzzling you, as I've phrased it like it is just dropping voltage, whereas I was only concerned with situations where we could be close to that maximum input current. Checking Philo's measurements, with his load (no idea how much it weight though), this motor consumes 360mA, which should be somewhere at 85% efficiency, so if I'm not horribly mistaken it would give around 850mA input current, so still below 1.2A. To summarize, I think that under heavy load (also when stalled), it could not be able to provide enough voltage for IR receiver to operate. Thanks for listening to my ramblings!

@Toastie Thanks! It seems like only my planned voltage regulator might be the weak part in the chain - under load (depending on input voltage), their efficiency varies, and voltage may drop below desired level and I just probably need to conduct that test to see if its enough :) Great to see so many tinkerer here:) Hmm, just one more thing @Toastie - those 3 AAs, are those rechargeable? (this would make it even less than 4.5v)

Cool! Not sure I understand your setup though, as you've mentioned you're powering 4.5 trains with this receiver. Just to be clear - what I mentioned is replacing battery box (9V) with 5V power source.

Just wanted to check whether someone has already tried it. I haven't yet got connectors to try it out (with my power bank), but I plan to conduct such tests. My scenario would be IR receiver powering train motor(which works fine with 5V).

Awesome! Since you had parts neatly packed and prepared, could you share se numbers? This thing look quite massive - how many parts it required? Have you bricklinked it? When I see various MOCes I can't stand but being curious how much it really cost, but people tend not to mention that;)

That breakfast better be good! I think you need one PWM pin, its pulses define the speed. But youre right I need to investigate pins, as more are needed to control the direction. As for the voltage - mind that 6 rechargeable AAAs you might have in your original battery box is 7.2V in fact. I think difference between 7.2 and 5V doesn't sound as scary as 9V and 5V. Check this: Not trying bigger step-up now - this whole idea resolves around powering everything with same 5V source.

Seeing couple of threads where people tried to electrify smaller builds to work with PF, the most problems were: * 9V batteries, which fit nicely, but have low capacity * bulky IR receiver I started toying with idea of using some small ATMega chip with IR receiver and powering everything by 4 AAA batteries, which then could be divided into two battery boxes for greater flexibility. But then I've stumbled upon following video, where they've suggested step-up voltage regulator with AAA batteries: After more googling and conducting some calculations, I've arrived at quite nice values: suppose we have 2 AA rechargeables, with 2600mAh, and we connect it to 5V step-up converter: 2 * 1.2V * 2600mAh = 6240mWh 6240mWh / 5V = 1248mAh and finally, apply the efficiency (about 80%): 1248mAh * 0.8 = 998.4mAh so about the same as with AAA rechargeables! So far so good, so let's see what can we do about this bulky IR receiver. Following http://www.hackvandedam.nl/blog/?page_id=547, it seems we need 4KB of flash memory on our chip, so author used ATTiny44a. Now, I don't want to fuss around with custom boards, I just wanted to plug everything with wires (some soldering might be in order, but I'm not proficient enough to make any board for it), so I want to use DIPs. ATtiny85-20PU could be the right choice. Obviously, chip can't drive the motor directly, so a motor driver like L293D (max 1.2A) would be used. Or better: SN754410NE. For the voltage regulation, something like https://www.pololu.com/product/2564. It handles minimum input of 0.5V (other regulators require minimum of 2.5V, which might not be achievable with rechargeable AAs), and maximum current of 1.2A (I keep to mention this current, because according to specs from Philo's homepage, the motor stalled current can be up to 1.3, but that's for 9V). Now, add the IR receiver (38kHz): TSOP4838. The page for voltage regulator mentions it would be safe to install the capacitor to prevent from sudden voltage spikes. So, my idea would be: 1. Connect the batteries to step-up regulator, from that the resulting 5V would go to: a) motor (via driver) b) ATtiny 2. ATtiny would be connected to a) IR receiver (not the LEGO one!) - operating at 5V b) L293D driver, the same 5V level would be used for the motor supply voltage, and for logic supply voltage Questions to those more electronically inclined: Do you predict any problem with such setting? Have I missed something?

Yeah, I don't want to make a board either (I have some soldering equipment, but almost zero soldering experience ;) ) - I'm just evaluating whether it would be possible to just connect all components with cables (I'd then buy the DIP version of chips). Edit: @bradaz11 - cool, I've checked some of those videos, in one of them he mentioned it would be better to use AAA batteries with step-up converter (to increase voltage), than 9V batteries. And it's quite a good idea I'd say, but one could even try it with AA batteries. Now, suppose we have 2 AA rechargeables, with 2600mAh (which, from what I've found, cost bit less than one 9V counterparts), and we connect it to 5V step-up converter (costs about the price of those 2 batteries), then, following calculations from this link, we could achieve 1248mAh, and with 85% efficiency it would still be above 1000mAh which would be quite awesome (hope I got that right ;P ) !

In the first link - yes there's full blown arduino there. What I had in mind is barebone ATTiny, which is...tiny;) (just realised there's no second link in my previous post - forgot to paste it: http://www.hackvandedam.nl/blog/?page_id=547) Even arduino nano is bigger than needed - it has microusb socket. Thanks for videos! Need to watch them. If you start something - I'm interested in your progress!

@Paperinik77pk - thanks! In the meantime, I got another idea, which might, or might not be crazy. What if instead of using bulky (and expensive) IR receiver one would use some ATMega controller? From what I know, the smallest of them, the ATTiny, is capable of PWM. This would require some additional circuitry, but maybe it would be doable without much soldering :P I stumbled on something like this: https://www.hackster.io/Notthemarsian/take-control-over-lego-power-functions-ee0bfa#toc-controlling-a-lego-motor-with-the-l293d-chip-1 My plan would be to replace the Arduino with just ATTiny chip (have to check if it would work without some additional resistors/capacitors), and then using 2 2xAAA battery holders. One such holder would fit in 2 x 7 x 3 area, so one could stuck them in the front and rear parts, leaving quite a lots of space in cabin for additional circuitry/cables. The disadvantage would be that it should be about 0.75 slower (because of lower voltage), but on the other hand it would last even longer :) (using 9V battery with such setup would cause problems because those chips operate on 5V level). The advantage - price (well, I haven't yet investigated prices of bluetooths chips properly) :)

Not sure what the actual image was, but here some people dissected it:

The project hasn't died yet! I've ordered the parts for the (almost) vanilla version, but not everything went as planned. I found out a shop where I could fetch those yellow window frames (which are seemingly fairly rare), and this shop had pretty nice discount going on (even for PF parts), so I started preparing order. Wasn't fast enough for a motor and IR, but I went on the bricklinking spree and it didn't turn out exactly "on the cheap" (but hey - I've heard you can never get enough straight tracks and switches, right? ;) ). Bricklinking is hard. I'm now left out without extension PF coord (to connect 9V battery), train motor and IR receiver for this, and with budget exceeded

Whoa! I've been recently thinking about it, as I measured one could hide 6 AAA batteries neatly in 2 stud wide, 3 bricks and 1 plate high nose of locomotive. Just wasn't sure how to attach the batteries so that they would be connected neatly and don't disconnect when shaken. Care to share some details? Edit: ah, I have been to fast with this reply, I see battery holders there as there's more space than I had.

@Paperinik77pk this is slick! The snot'ted semi plates might look a bit out of place in such model, but they're successfully hiding so much! (I'm wondering how well they're kept in place, the one closer to cabin is mounted on one stud). And you got away without introducing another color, so you were able to get her back to black, which looks great. Oh, and thank you for taking care even of such fine detail I hadn't thought of - square reflectors, which imitate original better. And all of this right after when I thought it make sense to build it like in original, only packing IR to the cabin, and 9V (16mm wide - so 2 studs width, and 3 bricks in height) to the front. And now I have no idea which way to pursuit;D would make sense to find out part that would allow building both versions. Please share the lxf, definitely :) Although I have no idea when it'll come to fruition - the spring has started, kids only want to play outside and I lack the excuse for buying more Lego...

Would be fair to state that IR tech more expensive than BT? Regardless, IR receiver is not *just* a receiver. It sends PWM signals to motor, so it's sort of a receiver-controller.

I've checked it, it...sort of works, but when you push the motor bogie towards the plate, you see that battery box is starting to detach. Whether it would be an issue in practice, I don't know.

It just means when I was looking for it via BrickLink (1 x 4 x 3 blue panel), I was unable to find anything that ships from my country, but now I know why - I've searched for part with "undetermined stud type". There's bit more of others (2 other molds), not *that* much though. Anyhow, this is worth pursuing. Not only it means less fiddling and changes to original design, but it should also be cheaper. I know it's gonna provide less hours of playtime, but whether it's annoying or not, that's something to find out.

@Selander In your 7760 thread, you've mentioned you used 1 x 4 x 3 panels to fit the 9V battery, and those aren't common parts. Was it necesity, or were you able to find 9V batteries that would fit without use of panels?

Yeah, I wonder - from what I've read it might rule out the IR receiver, which is supposedly now integrated into battery box. But - does this mean it's really tiny and fits in current size of battery box, or does it mean that...battery box is getting bigger :) ? As for other batteries - I've stumbled upon 9V (PP3) rechargeable battery at my household which is slightly smaller than standard one, and fits exactly in 2 x 6 x 3. Now, with thing like that, one could even try to fit it in small shunter like 7760. Haven't tried it yet though - don't have proper charger at hand.

Neat! Couple of questions: 1. Is the 2x2 plate behind IR receiver simulating cable plug? 2. Since you've followed suggestion to fit pin in the battery box screw hole, it might not be possible to move it to accommodate the cable... 3. (following 2) Does it really require "custom" base plate? Now, I don't have all the parts (especially in color), but I think I should be able to prototype the most important part of this.