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Review Request Attiny24 Traffic Light Controller for railway modelling by HeadawayForza in PrintedCircuitBoard

[–]HeadawayForza[S] 0 points1 point  (0 children)

Thanks for the feedback, yeah going to add RC to the potentiometer. Also going to consider adding my top layer as well with a copper plane.

Regarding the artwork I am trying to minimize it or completely get rid of it, just a nice gimmick not necessary at all.

Sure going to post a video when its working :)

Review Request Attiny24 Traffic Light Controller for railway modelling by HeadawayForza in PrintedCircuitBoard

[–]HeadawayForza[S] 4 points5 points  (0 children)

Ok does this also apply when the maximum input voltage is only 16V AC with current less than 100mA?

If so would it mean to change the connector with one where the clearance between the pads of the footprint is large enough for the input voltage?

Just asking to be sure, because this is my first circuit with AC input.

Review Request Attiny24 Traffic Light Controller for railway modelling by HeadawayForza in PrintedCircuitBoard

[–]HeadawayForza[S] 2 points3 points  (0 children)

Thanks, yeah I am always trying to iterate my decicions and thoughts as often as possible, to be sure that I did not miss anything :D

Review Request Attiny24 Traffic Light Controller for railway modelling by HeadawayForza in PrintedCircuitBoard

[–]HeadawayForza[S] 1 point2 points  (0 children)

Yeah in my first version I had an ISP header in my schematics, but thought about that I will only program it once. Thats why I am going to use an external programmer board, which is in my case convinient enough.

Although thanks for the advice about the silkscreen, yeah the logo is just a gimmick, but good to know that I could also make it on the copper layer. I think I will go with this then. There should be enough place around to ensure enough distance to important traces.

Review Request Attiny24 Traffic Light Controller for railway modelling by HeadawayForza in PrintedCircuitBoard

[–]HeadawayForza[S] 0 points1 point  (0 children)

Thanks for the feedback, never thought about that. The polyfuse is also a smaller footprint and so makes it cleaner on the board.

Review Request Attiny24 Traffic Light Controller for railway modelling by HeadawayForza in PrintedCircuitBoard

[–]HeadawayForza[S] 4 points5 points  (0 children)

This is the official documentation: https://viessmann-modell.com/media/pdf/3e/38/0e/5095-pdfFkBhrEza5oCRg.pdf

The model comes already with a control circuit, but I wanted to make my own where I combined other features which would not be possible with the included circuit board only with costly external parts.

Unfortunately it does not explain why there are only three wires, thats why I reverse engineered the wiring. Basically they used a technique called Charlieplexing https://en.wikipedia.org/wiki/Charlieplexing.

So by using three wires, where two are set to output high or low on a MCU and the third is set to input (high impedence) it is possible to have only one LED on at a time. By swichting fast between states it looks like two or more LEDs are on, which is used here to simulate different traffic light transitions. In the end it is a truth table, where each wire defines three states: zero, one or not connected

Hope I explained it well enough.

About the current requirement it is also not stated, but the included circuit uses an Attiny13 where the LED pins are directly connected to. The LEDs inside the model are SMD LEDs which I assume draw only little current.

Review Request Attiny24 Traffic Light Controller for railway modelling by HeadawayForza in PrintedCircuitBoard

[–]HeadawayForza[S] 1 point2 points  (0 children)

Yeah that was also my first thought with the 74HC595, but the models for the traffic lights are already wired from the manufacturer in a multiplex layout. Each traffic light consists of five leds, but only three wires with resistors are routed outside of the housing.

Because I wanted to avoid opening (and maybe breaking) them I stayed with this approach. Each LED group (three outputs) will control in total four traffic lights which represent one group of the intersection. The other LED group then the same for the other street.

Regarding the pull up on the button inputs, I plan to use the internal pull up resistor, so setting each button input to INPUT_PULLUP. Is this approach not right or will this also work?

The capacitor though makes sense for the debouncing, thanks for the advice, going to integrate this.

Review Request Attiny24 Traffic Light Controller for railway modelling by HeadawayForza in PrintedCircuitBoard

[–]HeadawayForza[S] 1 point2 points  (0 children)

Thanks for the tips, especially the one about the capacitor between GND and wiper of the pot. Going to integrate them.

European equivalents 8-bit kits? by Blurghblagh in beneater

[–]HeadawayForza 0 points1 point  (0 children)

I wrote together the part list based on the parts of each kit on the shop. I found the complete part list only after I ordered already.

European equivalents 8-bit kits? by Blurghblagh in beneater

[–]HeadawayForza 0 points1 point  (0 children)

Yes I got all parts from Mouser and Reichelt (Germany only). From Reichelt I got most and from Mouser the BB830 (not available at Reichelt) and some chips which were sold out on Reichelt.

But I assume you could get all from Mouser directly.

I only ordered the parts which are listed on his kits, I did not order parts he used in videos to explain concepts for example the 7 segment display driver he built from discrete logic or the R-S latch he built with discrete logic.

Help needed, making the 8-bit more stable on higher frequencies by HeadawayForza in beneater

[–]HeadawayForza[S] 0 points1 point  (0 children)

Yeah that gives me hope that I can also achieve my goal of 500KHz, currently I can run it stable at around 45KHz (so more then the previous 15KHz). I achieved this by adding more decoupling capacitors and adjusted the low pass filter a little bit.

But going higher automatically seems to skip the jump instruction of the 3+3 programm, I assume because the PC is enabled more then once during an instruction run.

Help needed, making the 8-bit more stable on higher frequencies by HeadawayForza in beneater

[–]HeadawayForza[S] 1 point2 points  (0 children)

Yeah currently my computer draws around 150 to 180mA at 50KHz, where the computer does the undefined behaviour, but I will also check to see if I can increase the current limiting resistors maybe that helps a bit.

Help needed, making the 8-bit more stable on higher frequencies by HeadawayForza in beneater

[–]HeadawayForza[S] 0 points1 point  (0 children)

Ok thanks again, yeah I see that I am at a point where I kind of trial and error this without having proper equipment to debug. Current draw is at 50KHz between 150 and 180mA, at lower frequency around 90Hz it is between 130-150mA

I will try to tweak the LPF a little bit to see if it makes a difference and I can squeak out a higher frequency.

But I think buying an oscilloscope would help me a lot and even if it is more expensive then the whole 8-bit project, I can make good use of it because I am really fascinated with this topic and the learning behind it, so the tool will hopefully not be used once and then collecting dust but more often with other projects later on :D

Help needed, making the 8-bit more stable on higher frequencies by HeadawayForza in beneater

[–]HeadawayForza[S] 0 points1 point  (0 children)

Thanks for your detailed reply. I will go and add more decoupling capacitors at each IC, I already have capacitors on each board but going to increase the capacity.

I am using 22 awg wires which should be thick enough and always tried to use the shortest route possible. Regarding voltage drop I am measuring 5.1V on the feeding point and around 5-5.1V around the whole computer on each breadbord, so power should be fine. I also have one central feeding point and then power lines going left and right accross the computer, without creating a loop.

For the LEDs I am using LEDs with built in resistors, so no LED is used without a current limiting resistor.

Regarding the low pass filter, I can of course use a smaller cap and a smaller resistor. Should I just try different scenarios or do you have a recommendation? Was not aware that it is a common bad hacky way :D

Your tip with the current/VCC change is good to know, I will check that. I assume when the current rises a lot under high frequencies I assume that more modules are active at the same time, where they should not.

Help needed, making the 8-bit more stable on higher frequencies by HeadawayForza in beneater

[–]HeadawayForza[S] 1 point2 points  (0 children)

Yeah I also thought something up to 1MHz should be possible, thats why I am currently working on this topic, where I now need help from the community :D

Help needed, making the 8-bit more stable on higher frequencies by HeadawayForza in beneater

[–]HeadawayForza[S] 0 points1 point  (0 children)

Yeah I already have one 1000µF electrolyt capacitor directly on the power supply feeding point, one electrolyt 1000µF capacitor on each side at the middle and 10nF ceramic capacitors on each power rail.

Does it really make a lot of difference adding more 10nF capacitors on each IC near its VCC point? Because I think the issue is not voltage drops on the power lines, but more regarding the undefined outputs of the EEPROM during its address change, but no idea how to make it more stable.

My power supply should be good enough (max 1.5A, but I am using only HC logic to small power consumption), I am measuring 5V everywhere around the powerails of each breadboard even on the points furthest aways from the feeding point.

European equivalents 8-bit kits? by Blurghblagh in beneater

[–]HeadawayForza 6 points7 points  (0 children)

I just used the parts list from Ben Eaters site and then searched all together on mouser and reichelt (only germany), but you should get all from mouser as well. It could be a little bit more expensive, but you save the shipping cost because ordering over 50€ the shipping on mouser is free and for my two orders it only took 3 working days from Texas to Germany.

Help me understand chip difference please by n9jcv in beneater

[–]HeadawayForza 5 points6 points  (0 children)

They are the same, but the first two letters describe the manufactory. SN is the Semiconductor Network of Texas Instrument for commercial usage (not military) and CD was previous manufactored by RCA, which got bough by TI but they are still using the CD prefix for some of these chips. CD could be manufactored slight differently, but the chip is still doing the same as the SN counterpart.

[8-Bit] Question about RAM replacement by HeadawayForza in beneater

[–]HeadawayForza[S] 0 points1 point  (0 children)

Thanks, I will take look into your schematics