Poll

How about creating a GitHub repository for this?

Not really interested
7 (70%)
Would like to take a peek at one
2 (20%)
Would like to use the concept, but mostly create stuff myself
1 (10%)
Would like to duplicate the modules as they are
0 (0%)

Total Members Voted: 10

Author Topic: Playable electronic modules - modules in action  (Read 9867 times)

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Offline HendriXMLTopic starter

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Playable electronic modules - modules in action
« on: March 03, 2019, 03:22:34 pm »
Hi,

I'm in the process of creating playable electronic modules for my son (9).
For logic gate circuits I bought IC’s from the HD74LSXX series. The attached example will for instance be using a HD74LS86P. This should be somewhat ESD safe…I hope

The circuits will be mounted in a 3D printed box, with a symbol sticker on top and the IC’s as a dead bug on the bottom with connections to the (5V) power rails with a 100nF capacitor and IN and OUT pins of the IC.

The power rail can be daisy chained (?). I already made wires that split from 1 into 3 connectors. I’ve chosen for female connectors because they’re a bit safer (more isolated) to have them unconnected.
The modules will be connected with 20 cm (silicone) wires. I don’t know if this is problematic.

Before implementing this, I would like to know if I’m missing something..

Feel free to comment!
« Last Edit: March 16, 2019, 02:53:23 pm by HendriXML »
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Offline HendriXMLTopic starter

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Playable electronic modules - stickers ready
« Reply #1 on: March 03, 2019, 07:37:36 pm »
I created all of the IC sticker (vector)drawings.

If someone is interested in those, let me know! The price per module is less than 1 euro all inclusive (my guess), so these toys will not become expensive. It will (probably) eventually evolve into stuff that can also drive Lego Technic.

They match a 5x7cm perf board. I'll laserprint them on plastic stickerpaper (AliExpress). In combination with Visio that stuff is also great to transfer very accurate measurements/positions of objects.

It is less sharp than printing on normal paper, but it can handle much more abuse.
« Last Edit: March 03, 2019, 11:38:38 pm by HendriXML »
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Offline ebclr

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Re: Playable electronic modules
« Reply #2 on: March 03, 2019, 07:43:36 pm »
Your sun will fell more fun on playing with this https://www.labcenter.com/

 

Offline HendriXMLTopic starter

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Re: Playable electronic modules
« Reply #3 on: March 03, 2019, 07:58:08 pm »
Your sun will fell more fun on playing with this https://www.labcenter.com/
Maybe, but these kids to day do a lot of virtual activities. I'd like to encourage him to do also real world stuff, with real world problems (and problem shooting) and these modules are a small step towards to that.
« Last Edit: March 04, 2019, 12:50:14 am by HendriXML »
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Offline OM222O

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Re: Playable electronic modules
« Reply #4 on: March 03, 2019, 08:01:31 pm »
one suggestion would be to use small perf boards which can be daisy chained together rather than using the "6 gates in one box" approach. if you have each gate on a separate, smaller board, the wiring for more complicated projects in the future will be a lot easier, but using a box approach your wiring will become a spaghetti monster :D also you can put LEDs both on the inputs and outputs so it's more obvious how each gate is behaving.
 

Offline Gyro

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Re: Playable electronic modules
« Reply #5 on: March 03, 2019, 08:08:59 pm »
I remember back in the '80s one of the UK electronics magazines (I think it was Practical Electronics) gave away a sheet of DIP IC sized stickers that could be put on top of standard 74 series logic. They were small but readable, it seemed like a pretty good idea at the time.

Of course they didn't provide enough stickers for each part - I can't remember if it was a commercial idea that never took off.

You could maybe revive the idea though, to make it compatible with ICs on a breadboard rather than large modules.
Best Regards, Chris
 

Offline HendriXMLTopic starter

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Re: Playable electronic modules
« Reply #6 on: March 03, 2019, 09:02:28 pm »
one suggestion would be to use small perf boards which can be daisy chained together rather than using the "6 gates in one box" approach. if you have each gate on a separate, smaller board, the wiring for more complicated projects in the future will be a lot easier, but using a box approach your wiring will become a spaghetti monster :D also you can put LEDs both on the inputs and outputs so it's more obvious how each gate is behaving.
I've made some early prototypes (with only transistors) and have seen what you say to be true. However not all gates need to be used, they're all exposed because they come free  ;D. One positive thing about larger modules is that they stay flat when making use of flexible silicone wires.

However this whole "project" needs to evolve. It starts educational and probably ends more practical.
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Offline HendriXMLTopic starter

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Re: Playable electronic modules
« Reply #7 on: March 03, 2019, 09:26:10 pm »
you can put LEDs both on the inputs and outputs so it's more obvious how each gate is behaving.
Had that in mind also, but that would need to be implemented in a very elegant way, otherwise it becomes a bit to intimidating. With the split wires one it is possible to lead a debugging one to a led on a other module. Debugging is a skill as well  :-+
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Offline HendriXMLTopic starter

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Re: Playable electronic modules
« Reply #8 on: March 03, 2019, 09:26:51 pm »
I remember back in the '80s one of the UK electronics magazines (I think it was Practical Electronics) gave away a sheet of DIP IC sized stickers that could be put on top of standard 74 series logic. They were small but readable, it seemed like a pretty good idea at the time.

Of course they didn't provide enough stickers for each part - I can't remember if it was a commercial idea that never took off.

You could maybe revive the idea though, to make it compatible with ICs on a breadboard rather than large modules.
Thought of that too  :-+

The current approach is certainly not space efficient.
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Offline HendriXMLTopic starter

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Re: Playable electronic modules
« Reply #9 on: March 03, 2019, 10:50:10 pm »
Made a schematic and PCB layout in KiCad, just not to get lost....

Having done that, I think the module is a lot easier to wire :popcorn:
« Last Edit: March 04, 2019, 04:35:53 pm by HendriXML »
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Offline HendriXMLTopic starter

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Playable electronic modules - soldered
« Reply #10 on: March 04, 2019, 03:39:13 pm »
I finalized the soldering of 1 module.

First time using lead free solder.. (The toy is boxed, but better to be safe. Don't know whether the perfboard is lead free anyway. )

I had to take care not to heat the plated holes to much. Had to clean solder once and then the plastic sticker locally melted. Besides that it went well, but it is very time consuming for something that supposed to be cheap :P.

Only used 2 isolated wires. Most of the connections on the IC are made by creating a small wire loop at the end of an thin wire to keep the thicker wire and IC pin together and soldering those 3. Should make desoldering easier. But it is probably still a lot of work to replace the IC.

Maybe on the next one I will do the IC first, then the sticker and finally the pinheaders.
« Last Edit: March 04, 2019, 04:59:11 pm by HendriXML »
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Offline HendriXMLTopic starter

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Re: Playable electronic modules - soldered and tested
« Reply #11 on: March 05, 2019, 01:19:29 am »
The PCB is now mounted in a 3D printed box, it has inside 4 stands in the corners of 10mm: high enough for the dead bug not to get crushed.

Had ordered some of those hex screws (AliE), I think they look great. They're not really needed because I had to squeeze the PCB in, but now I know it stays in  :-+.

For complete DIY and the low cost I'm happy with the result.

It is quite sturdy and relatively heavy.
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Offline HendriXMLTopic starter

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Re: Playable electronic modules - soldered, tested and boxed
« Reply #12 on: March 05, 2019, 11:02:23 am »
While testing the module I found the inputs to be very sensitive when not connected.

Can I leave them floated or is pulling them to ground with let’s say a 10k resistor “obligatory”?

And what would be the highest resistor that is still functional? I choose a 10k because then the current loss is still doable when a lot of inputs are in use.
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Offline Gyro

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Ah, that's something that one of us should have picked up on.  :-[

Firstly, yes, floating inputs are bad on cmos logic. I think you could safely go up an order of magnitude to 100k on the resistors.

That brings me to...

1. Input protection - you may want to add protection diodes to each input for static protection. Maybe overkill, socketing the IC might be an easier solution.

2. There are no VCC and Gnd pins on the box (aside from the PSU headers, which I assume you intend to daisy-chain). You are very likely to want to tie one or more inputs high or low when experimenting. You probably want to provide 4 pins of each.
Best Regards, Chris
 

Offline OM222O

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Yes, as Gyro mentioned, either use TTL logic instead of CMOS (more power draw for more gates if floating inputs are a bigger issue)
or tie them to ground with 100k (47k to be on the safe side) if random readings on floating inputs are a bigger issue. it comes down to how large the project is and how lazy you are. I would personally stick to TTL as it's unlikely for you to be using lets say 500 gates at a time? even ben eater (youtuber) made a full 8 bit breadboard computer using TTL series logic and the power draw wasn't too bad. that will also saves you cost of the resistors (although fairly cheap) as well as soldering them in one by one (my main point of laziness lol).
 

Offline HendriXMLTopic starter

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I thought I bought the TTL logic stuff looking at this website https://www.electronics-tutorials.ws/logic/logic_7.html.

I also ordered CMOS IC’s with the same gates like the TC4030BP.

On the introduction page https://www.electronics-tutorials.ws/logic/logic_1.html it says on the LS series:
74LSxx: Low Power Schottky TTL – Same as 74Sxx types but with increased internal resistances to improve power consumption. Supply voltage range: 4.75 to 5.25 volts

So I’m a bit surprised with them beeing so sensitive.

Did I buy old school stuff which is too “modern”?

I’ll add the resistors. This however will make the modules even more time consuming.  :palm:
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Offline HendriXMLTopic starter

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There are no VCC and Gnd pins on the box (aside from the PSU headers, which I assume you intend to daisy-chain). You are very likely to want to tie one or more inputs high or low when experimenting. You probably want to provide 4 pins of each.
That’s a good idea. Will add some boxes with just that, and proper symbols and all. I already have 1 module with dipswitches wich can give either high or low. A more user friendly module with larger buttons and toggle switched will follow.
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Offline Gyro

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Damn, I didn't notice from your OP that you were using bipolar 74LS series. In that case your 10k is about right, but pulled UP to 5V rather than down to GND. Bipolar LS TTL logic has very unequal high and low currents (Input : about 20uA high and 360uA low, Output: 400uA high and 8mA low).

It is much harder to pull an LS TTL input low with a resistor, you need to achieve no more than 0.8V with the 360uA input current flowing. If you pull up then you only need to get above 2.7V with 20uA flowing. If you try to use pull-down resistors then your other gates will have difficulty overcoming them with their relatively weak output high capability. Floating (unconnected) bipolar TTL inputs are an old trap, they float high on their own but are very sensitive to noise.

In the same way, if you want to drive an LED from LS TTL, then you put it (and its current limiting resistor) between the output and +5V. This means that it lights on logic low.

This may a get a bit confusing for a young mind (it made my head spin a bit just typing it!). I really suggest that you consider using CMOS 74HC logic instead. Its input current is symmetrical at <1uA (hence 100k resistor) and the outputs are also symmetrical at +/- 4mA. It is more static sensitive, but not as much as modern low voltage CMOS. Its 2 - 6V VCC and very low supply current make it much more battery friendly too.

Sorry for the confusion. I've linked a 74LS00 datasheet and 74HC00 datasheet for reference - they are representative of their respective logic family electrical parameters.

http://ecelabs.njit.edu/student_resources/datas/74ls00.pdf

http://pdf.datasheetcatalog.com/datasheet/on_semiconductor2/74HC00.PDF
« Last Edit: March 05, 2019, 05:08:24 pm by Gyro »
Best Regards, Chris
 
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Offline HendriXMLTopic starter

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Thanks, you give a lot to think about. I’ll study the datasheet, but also do some measurements in pulling up/down.

Having inputs which need to pulled down is probably also handy when using comparator modules.

Battery life I’m not really concerned with yet, if some experiment is worth running for a long time it’s probably better to make a dedicated circuit for that using more optimal components. Otherwise the modules will be “in use” to much, increasing the need for more of them.
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Offline HendriXMLTopic starter

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It is much harder to pull an LS TTL input low with a resistor, you need to achieve no more than 0.8V with the 360uA input current flowing. If you pull up then you only need to get above 2.7V with 20uA flowing.
What you say is also explained in more detail here https://www.electronics-tutorials.ws/logic/pull-up-resistor.html for those interested. The difference between pull up/down is so large, that I’m not going to measure voltage drops :-+ 15k Pull up it will be!
« Last Edit: March 05, 2019, 11:20:55 pm by HendriXML »
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Offline HendriXMLTopic starter

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Re: Playable electronic modules - soldered and boxed
« Reply #20 on: March 06, 2019, 12:42:50 am »
The resistors are doing pull ups. I call them pull up resistors.

Also added an extra cap, because the modules may get long power wires while chaining them.
« Last Edit: March 06, 2019, 08:34:35 am by HendriXML »
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Offline radix

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The toy looks interesting, but I keep having thoughts about something. Be careful that the modules aren't left lying on the floor. Stepping on one would hurt much much more than stepping on a lego. :) Maybe you should think about right angle headers...
 
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Offline HendriXMLTopic starter

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The toy looks interesting, but I keep having thoughts about something. Be careful that the modules aren't left lying on the floor. Stepping on one would hurt much much more than stepping on a lego. :) Maybe you should think about right angle headers...
The modules know how to defend them selves  :-+

But you’re absolutely right, stepping on Lego is unpleasant, stepping on those pinheaders would get bloody. Thanks for pointing that out. I envisioned the modules to be played with at the kitchen table, but that being obligatory is a real disadvantage.

Angled headers would be much better in this regard, but are also more inconvenient. So I need to give this one more thought.
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Offline OM222O

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Re: Playable electronic modules - soldered and boxed
« Reply #23 on: March 06, 2019, 11:32:09 am »
Just a side note: you can get 10 PCBs for 2$ from jlcpcb (+ shipping which depends on what you choose). I think that will end up being more convinient and actually lower cost rather than using a perf board and wires to solder everything together. You can print and put the symbol of the gate on the top as well so the same pcb can be reused for all of the gates. It' also a lot easier if you want to add leds on the inputs/outputs.
 

Offline HendriXMLTopic starter

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Re: Playable electronic modules - soldered and boxed
« Reply #24 on: March 06, 2019, 11:45:02 am »
I found a graceful solution.

First the direction of the modules will change 90 deg (thus portrait). Inputs on the left, outputs on the right. This will give a better view on the sticker. (And follows a common design rule.)

The headers will move to the edges. Where they are sided with a 3D printed wall (5mm thick).

The powerheaders will also move, one on the topleft and on on the topright edge.

Maybe I can make the modules click to each other with magnets, there would be room in the walls for that. However 3D printing holes in that direction is not very precise.
“I ‘d like to reincarnate as a dung beetle, ‘cause there’s nothing wrong with a shitty life, real misery comes from high expectations”
 


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