Repairing (a possibly common?) Serial Communication Issues on LEGO Dacta Interface-B

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Edited June 27 by Gunners TekZone
Removing dead image links

[Toastie]

7 hours ago, Gunners TekZone said:

And behold, Again!! That worked!!!  

@Gunners TekZone

CONGRATULATIONS! I knew you could do it (provided the Siemens 1001 feet chippie wouldn't be in Chip heaven).

Really nice to know. So that means the built-in serial to TTL chip has gone bye-bye, right? Did you need to take that "away" from the RX/TX lines of the microcontroller?

Very nice!!!

All the best,
Thorsten

[evank]

12 hours ago, Gunners TekZone said:

I truly hope this will help others with a "mostly dead" Interface-B to take a closer look and poke around.

 

[Bliss]

@Gunners TekZone, wow you're da man!

Not much people still play with those Interface B but they are quite unique in some way as they offer the most quantity of inputs and outputs in one box...

And if you can connect 3 or more on a same PC interface, it offers 24/32 Inputs and same for outputs all available in one programming environment to achieve big projects.

I have an EV3 kit but never opened it yet...  So I don't really know how it can expand itself and interact with other EV3 or other systems...
But I see these RCX, EV3, NXT more like small standalone controller that have there own independant program and very limited IO capability...
I understand that like the RCX, EV3's probably have a way to send messages between each other but it's not the same...  Can one EV3 expands its IO capacity somehow?

Did lego completely stopped production of mindstorm?  I see today in their education line some spike and BricQ ?  technic hub?  EV3 is marked retired.  I'm clearly behind on this :-)
Are they working on a new version?

That would be great if they could enter the IoT world making wireless sensors using battery button like zigbee and BLE stuff...  (Touch, light, temperature, IR motion sensors).  (Wires can be a pain in projects)

Is there a thread about what would be the best new Lego Smart System for you ?

I think I saw on TikTok, lego projects using motors and electronics I've never saw in a lego store...  Third party bricks?

 

Edited January 17, 2025 by Bliss

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Edited June 27 by Gunners TekZone

[Bliss]

What would be great is to have an easy solution to get rid of the Serial data cable and the PSU 12VAC 7VA.
So removing the RS232 circuit and replace by a FTDI USB input USB-C or USB-A. 
And, use the 5V from the USB with a step up board to provide 9vdc at about 1A or less.  I don't know what the lego outputs capacity...  but 7VA is not much... 

I think a USB port on a computer should be able to supply the whole thing no?

 

Edited January 17, 2025 by Bliss

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Edited June 27 by Gunners TekZone

[Toastie]

39 minutes ago, Gunners TekZone said:

At this time, I am debating ways to use the original cable to transmit the signals from the CPU to the USB-TTL Serial Adapter, which I hope will physically replace the DB9 connector... if it fits.

Well, then I sure hope it does fit!

I am planning to go partly wireless (Bluetooth) on all my control boxes (2 x 8485 CCII, 2 x 9750 and 1 x 9751). So far, my modified 8485 (), which behaves more or less like the outputs of 9750 has currently such a BT thingy (https://www.eurobricks.com/forum/index.php?/forums/topic/192941-lego-interface-a-97509771-–-lego-technic-control-1-tc1-referenceideas-thread/&do=findComment&comment=3734005). 9751 also does 9600 Baud. Why don't you hook up an HC05 directly to the TTL RX/TX lines (with a 1k/2.2k voltage divider on the TX=input from 9750, HC05 are 3.3V, but tolerate 5V VCC; and the RX of the Siemens chips will be happy with 3 V TTL input)? The 5V are available inside 9751.

Result: No more cables, just the power cord of 9751. Well, I'll try and report back ;)

All the best,
Thorsten 

16 minutes ago, Bliss said:

I think a USB port on a computer should be ably to supply the whole thing no?

Hmm. The brain, for sure, but 8 x 9V motor outputs? ... maybe two motors stalled - that would add up, doesn't it? Philo's page suggests it would.

I just replaced three "12V" AC wall warts (they generate anything between 12 and 16 V of course) with one 12V, 8A old-fashioned incandescent Christmas lights PSU weighing a ton, which I got from my neighbor - he said, it may be of value to me . That one powers my 8485, 9750 and 9751 boxes. 

I would not so much have my laptop providing motor power via USB, but I could work, of course!

Best,
Thorsten

Edited January 17, 2025 by Toastie

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Edited June 27 by Gunners TekZone

[Bliss]

The original Lego PSU is 12VAC 7VA so we talk basically of 600mA at 12 VAC for the whole box...  It not much...

Can the Box use more amps if we connect a bigger PSU say 12VAC at 2A (24VA)?

No matter USB-C or USB-A, from a computer port it is not like a PD Charger I think...

I would use the USB from a computer to have both DATA and Power.

But anyway, saying this, google tell me:  Most computer USB ports supply 5V of electricity with a maximum current of 0.5A.

So maybe not enough to use the interface at least like the spec...  but still...

Edited January 17, 2025 by Bliss

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Edited June 27 by Gunners TekZone

[Toastie]

3 minutes ago, Bliss said:

Can the Box use more amps if we connect a bigger PSU say 12VAC at 2A (24VA)?

Well, fortunately, we have our hardware guru @Gunners TekZone at work: What type are the H-bridge drivers inside the box? As I don't bet: I think they can deliver more than 100 mA each?

Best,
Thorsten

1 minute ago, Gunners TekZone said:

But stuff that already needs repair is fair game :P

I totally agree! My take as well.

Best,
Thorsten

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Edited June 27 by Gunners TekZone

[Toastie]

18 minutes ago, Bliss said:

The original Lego PSU is 12VAC 7VA

On another thought: The LEGO PSU for 9750 is also a joke, considering what they soldered as MOSFET drivers into the output circuits: 2x MTP3055's ... they can handle >10A each ... 

I guess they just wanted to be on the safe side. I mean, a 12 Wall wart just bends over when currents go crazy ... but the box can handle more, I believe.

Best,
Thorsten 

 

Lotsatraffic here

Nice photograph!

You'll find the data sheet on Philo's pages as well (https://www.philohome.com/motors/mlx10402.pdf) - they do 500 mA each; x 8 = 4A max.

Best,
Thorsten

Edited January 17, 2025 by Toastie

[Bliss]

Is there a fuse or other protection inside?

I'm certain that with the original PSU, 8 outputs of interface B cannot power 8 X 9v lego train.

But could it do it if we use bigger PSU?

Of course, the thin board power trace must be able to take it...  (I'm pretty sure it cannot take 10A though)...  But maybe 2Amps?

 

Edited January 17, 2025 by Bliss

[Toastie]

1 minute ago, Bliss said:

Is there a fuse or other protection inside?

The MLX 10402's have current limiters inside the chip.

Best,
Thorsten

[Bliss]

I see so 4A total for 8 outputs, but the box must allow it.

So is there a main protection at the power intput of the interface?

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Edited June 27 by Gunners TekZone

[Toastie]

2 minutes ago, Gunners TekZone said:

Thus I stay mostly at a hobbyist level.

OK, then your hobbyist level in your world is guru level in my world!

8485 = Control Center II, 9750 = Interface A, 9751 = Interface B ... for some reason I can recall numbers and images - nothing I am proud of, it simply is what it is. Sorry.

Best,
Thorsten

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Edited June 27 by Gunners TekZone

[Toastie]

22 minutes ago, Bliss said:

So is there a main protection at the power intput of the interface?

There is a L78S09 as 9V regulator = 2A max. or it will limit current. So this is it, I guess: 2A.

No fuses, just the active power controllers (78** and H-bridge chippies).

It is the same in 9750 - the MOSFETs can do 10A each, but the linear 4.5V power driver is a BDX34B = 10A max. The Interface A is one power monster - totally dumb, "just" a TTL driver (plus ingenious sensor circuits), but so nicely designed! I believe they had to do it as a) the olden days were better and LEGO was unbreakable and b) 4.5V motors easily stalled.

Best,
Thorsten

Edited January 17, 2025 by Toastie

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Edited June 27 by Gunners TekZone

[Toastie]

5 minutes ago, Gunners TekZone said:

It is mostly that all my memories get jumbled up without other clear marker clues or recall procedures.

It is good to know that. Because then I won't use bloody numbers but names or "descriptions" (as good as I can, I am wildly guessing here) when asking you for a favor or suggesting some things. Which is so easy to do. You know, every now and then, there are students in my classes having diverse health issues, and every time we (together) have worked out something to get them trough. Time - is relative. I love "success" (define success - it is a myriad of things that may or may not - evolve). Regardless of time. As far as I have read your messages on EB, you have provided so much insight, I would have >never< ever figured out.

Hey, like to come over to Germany and have fun in my group? I'd hire you right away. And I am not joking (as I enjoy so much to do under other circumstances).

All the very best, and with a bow
Thorsten

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Edited June 27 by Gunners TekZone

[Toastie]

34 minutes ago, Gunners TekZone said:

I better get working on my teleportation skillz

Just let me know what I have to install on my side - no, no wait, the Star Trek folks teleported without any device present on the target site. OK, tell me when you need some free space/area, I clear that.

Best,
Thorsten