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Frank N. Furter
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Posted: 14 May 2018 at 5:00pm | IP Logged Quote Frank N. Furter

Hi Grogster,

with your assumption about "Z" you're not quite right. On this (German) page you will find some information about Z-decoders.

...I use"Z" but without DCC... (My goal would be to make the system itself "intelligent" and to control the track sections with Micromites...)

Frank


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Grogster
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Posted: 14 May 2018 at 5:07pm | IP Logged Quote Grogster

Danke.

Well, blow me. Who would have thought. That is REALLY small. I did not think you could get any DCC into Z scale!

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Posted: 14 May 2018 at 10:14pm | IP Logged Quote Grogster

Time for some sleep, but this is what I have so far:





This board contains a MM2 and an SOIC H-bridge to drive the motor. Input can be AC or DC. Current PCB size is 31mm x 13mm - same width as an HC-12 module, and a little shorter. PWM 1A connects to the P pad(for engine lights, perhaps?), and PWM 2A/2B are the motor control PWM channels. The 2x4 pin-header holes are for the ICSP and console connections, although, you would not install the pin-header, as it would make the module to thick. We need to keep a low-profile.

I am thinking about making that 2x4 header into an edge-connector rather then pin-header. This will allow me to shave a few more mm off the length of the PCB, and then you just plug the PCB into an edge-connector socket for programming.

To be continued. Right now, I need sleep.

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Posted: 15 May 2018 at 10:54am | IP Logged Quote Grogster

Have changed the 2.54mm pin header, for a 1.27mm female header. These are half the size(obviously), and are only 4mm tall, so they should not get in the way, and this allows easy mounting on a matching jig for programming and testing.







Size is now 27mm x 13mm, so I have shaved 4mm off the length.
Passives are 0805, regulators are SOT-89, MM2 is SSOP, H-bridge is SOIC.
12v power can be supplied via the header, really just to make programming easy, as that allows the on-board regulators to do their thing without any kind of back-feeding issues. I will keep looking for ways to optimize this layout, as I want to get it as small as possible. I think this is pretty close to as small as we can get it though, without going to four-layer. I'm not prepared to go four-layer just to shave a couple more mm off the size, as four-layer boards are four times the price of double-layer.

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Posted: 15 May 2018 at 12:14pm | IP Logged Quote MicroBlocks

If you put the cap (100n next to the mm) to the other side you might be able to shave off another millimeter or two. :)


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Posted: 15 May 2018 at 1:24pm | IP Logged Quote Grogster

Nice one, thanks.

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goc30
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Posted: 18 May 2018 at 10:14am | IP Logged Quote goc30

i have seen this
esp32 + L298N
http://mail.ruisantos.me//l/VG075pY6dV4S1RmWyqb2Ow/jWduL1q4eulbERaJ6r763Arw/krxy06MpuSagC5CYou8Baw

it seem that it is too big for DCC
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Posted: 18 May 2018 at 11:16am | IP Logged Quote Grogster

Clickable link.

Too big. Agreed. I don't know how they plan to get all THAT into a model! I suppose if you were using a large-gauge scale or something. But they show it all hooked to one of those small 3v motors, so.....

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Posted: 18 May 2018 at 4:17pm | IP Logged Quote goc30

Thanks for the correction, I forgot.
Regarding the driver circuit, we do not need such a radiator or these big connectors, but it's still a bit complicated
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Posted: 22 May 2018 at 10:24am | IP Logged Quote Grogster

The decoder PCB's have arrived, and I am very happy with the final size. I have yet to build one, but I hope to do that sometime this week and have a play around with some code on the MM at the heart of it.









The decoder board is designed to interface with an HC12, which is why one is shown in the photos with it. The board was not designed to stack with the HC12, as that might have made the overall arrangement too thick, so the decoder and HC12 will be joined with short linking wires - I will upload more photos once I have one assembled.

I plan to use the clone HC12's for this project, as although they are off frequency, they will be fine for this kind of thing.

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