a display driver that connects to that flat ribbon cable to the display.
a MCU or computer to host your programming and send commands to the display driver
power, wether it’s battery, USB, or induction…
You can separate the screen from the driver and have the e paper show the last image. The one thing I’d be worried about is how fragile the components are on the side of the rapper display itself as well as the ribbon cable.
Also, you mention 150+ cards. Think of the time it would take to change each one separately with a dock. Connecting the display to the driver is not hot pluggable you would likely need to power cycle the whole thing at every card. Plus the damage risk of constantly connecting the fragile connectors.
Thanks, I was aware of some of those obstacles. But this adds a little more detail, to the point where I don’t think it would be economical to repurpose this for this. It sounds like my idea may be possible with current off the shelf tags, but I think the dock would end up being way larger than I was initially imagining. It also seems like I am looking at like a minimum of $500 in parts for a prototype, even if I were somehow able to get the tags for $2 a piece.
You misunderstand the dock interface. The plan would be to insert the ribbon into something more durablee to bridge into the dock to be more like a cartridge. The dock will be expensive as I would plan for either all or most of the “cards” to be docked at once. It wouldn’t be a insert, wait, insert wait, instead it would be insert all the cards into their slots after play.
I also realized that the dock will need to be a little more complex then I originally thought as well. A lot of games have extensive burn and draw mechanisms leading to an extensive set of cards. What you could do is only have the amount of cards you would need in the base set for most of these games that are actually in play at any given time. The rest of the “cards” could be held in the “docks” memory, then “printed” when you draw a new card. It would add a little bit of time to the games, but you could dramatically cut the amount of physical “cards” or tags you need for many games.
You could potentially modify a game to work with those cards. Making cards able to change state or add extra states (that would usually be extra cards) to a single screen. I like your idea. Maybe the idea would not be a retro fitting but a ground up new mechanics for the mage?
I think your best bet is to look for an appropriately sized electronic shelf labels, there are companies that specialise in them and they are already quite thin, battery powered and have bluetooth or nfc connectivity to change images.
Thanks I did try before, but now I had success. I stumbled upon those little price tags stores use to digitally update prices. Those could possibly work for this.
Is certainly in the realm of feasibility, at least in a technological level. You can get flexible e-ink displays that are less than a mm in thickness. Typically the hardware that changes the display is the bottleneck on size.
That being said, I have doubts about the idea of “manufacturing for cheap” as even small e-ink displays can cost $20+.
I did find some 1mm price tags on Alibaba for 3-5$ which could possibly be repurposed. The issue is I really would like to get the price driven down to $2-1, maybe even less… I want this thing to be able to mimic any kind of card game, and some of them have up to 300 cards… I think the plan would be to have 150 card sets. That would cover a lot of games, and if your playing a really nerdy game that does need 250+ cards or something there is a chance your friend might also have a set.
If you could get the price tag $300 or less you could probably get a lot of hard-core tabletop card gamers. I know thats a huge price tag, but the product isn’t meant for the masses.
But once the display is updated, the circuitry isn’t really necessary. Maybe you could reduce the thickness and the duplication of circuitry by having a “dock” with the circuitry where you insert the card to update it.
That’s exactly the idea! They would have pins somewhere on the buttom, you would plug all your “cards” into a dock that would act as a carrying case. There would be an open source website where people can design different games and then you choose one of the games and it refreshes all the cards to whatever game you want to play.
That’s the idea anyway, whether it’s feasible for something people are willing to pay is a different question.
I found a few references to this exact model on candlepowerforums.com which I believe has more folks who own(ed) incandescent lights. Not that has been such a long time, but LED technology advanced very quickly. Not sure if that will help your search.
My opinion: look for a new LED flashlight. It will have the proper circuit and design to take advantage of LED capabilities including high brightness, PWM dimming, power efficiency, and heat management. Adapting an incandescent flashlight will always be a compromise in one of those.
Edit: I have a similar flashlight and I bought a tiny usb-c rechargeable flashlight that is brighter for 1/5 of the size. And for battery life, you can recharge your keychain size light with any usb battery pack.
Yes, feature and price wise that would be the best decision… but I kinda feed bad trashing a perfectly good machined aluminum piece just because of a bulb. :(
Thanks- I got the thing running through a breadboard power adapter of all things, to confirm the pump was still living, so I will try what you linked! I am beginning to wonder if I wired my last adapters’ poles. So, this might have been user error on my part, doh!
What did you hook up? You mentioned using cords? But first off, what you pictured, you need to make sure it’s wired correctly. There is no standard for barrel jacks. The center pin can be positive or negative and the jacket and be positive or negative. If you’re using a generic 5.5x2.1mm female barrel jack most generic 12v power supplies overwhelmingly do center pin positive and jacket negative. Once you get polarity correct check the amperage rating of the supply and the motor. Motors usually require huge in rush current to start and can easily trigger a short circuit protection on the supply output
My gate driver is fairly crude but you could probably make something a bit better with a PNP transistor and either pull it down or leave it floating, or instead use a szaiklai pair
It is an N channel FET. The concept is called “bootstrapping” since Vgs needs to be greater than Vth for the MOSFET to be on. When the FET is on the high side and you want the full 9V on the output, you use the diode to charge the capacitor, and the other side of the cap is 0V. Then, when the other side of the cap is connected to 9V, the charge on the cap can’t go anywhere so the voltage on the other side jumps to 18V. This creates a Vgs of 9V. Ideally you would have something better to drive the gate to fully turn off the FET, but I just used a quick and dirty driver where the bootstrap capacitor directly feeds the gate instead of being the input to the driver. Because if this, the Vgs doesn’t drop completely to 0
I won’t be using this for my measurement issue (the other options are much simpler, and i was aiming for less parts, not more), but I’ll do some experiments to familiarize myself with bootstrapping
You could probably increase the 82K and 10K resistors to be much bigger (by a factor of 10x or maybe even 100x). Lookup the input impedance for the ADC of your model of ATmega, as long as it’s >10x the size of your resistors then your circuit will probably be accurate enough.
A couple more things to keep in mind:
a fresh alkaline 9V battery is actually 9.6V or more, not 9V.
9V battery voltages droop noticeably when under load because of their high internal resistance. Make sure to measure under the same conditions.
You could probably increase the 82K and 10K resistors to be much bigger
That’s what I thought initially, but this stackoverflow post dissuaded me. The argument there is that the measurement will be wrong, if the input current is not enough to charge the internal cap within the measurement period. But I’ve done some testing now, and measurements done with 820k and 100k agree well with what my voltmeter measures, so I’ll go with this solution!
a fresh alkaline 9V battery is actually 9.6V or more, not 9V.
Indeed! 9.6V * 10k/92k = 1.04V is still below 1.1V, so I should be fine in this case :)
9V battery voltages droop noticeably when under load because of their high internal resistance. Make sure to measure under the same conditions.
This is a good point!
My firmware will be pretty monotonic though, basically:
wake up
measure battery
measure some other sensors (the actual task of the device)
turn on a transceiver, send all the measurements (including battery voltage)
turn off transceiver & go to sleep
So, the load should be always the same at step (2).
From the stack exchange post: " 10 kΩ or less source resistance is recommended, otherwise the low pass filter effect of the capacitor with the source resistance becomes a major issue, requiring a longer sampling time for conversion and as a result limiting the maximum frequency."
In other words: a higher source impedance (caused by large resistors) is only going to drastically affect the results when you need to take fast repeated measurements (e.g. an AC source)
Could you do similar to diagram 2, but instead of an N-FET use a P-FET between the battery and first resistor in the potential divider?
Add a gate pull up resistor to source to ensure the FET is off by default, have the micro pull the gate down to take a measurement. You’ll probably need to add another resistor on the control pin to 0V to limit the voltage there also, but those two can be much much higher values to really limit current. Or use a zener/TVS diode instead of second resistor to clamp the voltage instead of dividing (more robust).
Switch it with an NFET
The micro will see 0V or divided/clamped battery voltage on the measurement pin.
Not sure I understand this point. Which resistor would you replace with a diode?
Sorry, I think I was talking nonesense (doing this in my head and just woke up 😅).
Not sure it’ll work with just a P-FET actually. You’ll likely need to control the PFET with a NFET, otherwise you still end up with too high a voltage on your control pin when the FET is off due to the gate pullup (unless you can use a fet with a very high Vgs Threshold and then drive it push/pull from the micro, but this isn’t really best practice).
The above comment about diodes was to protect the microcontroller pin, but you end up not being able to control the FET doing it that way.
I think either your existing Option 3 or PFET upstream of the divider, switched via an N-FET is the way to go.
Well, you could say that there are three branches of electronics: analog, digital, and discrete (sort of between the previous two). For your goals, you mainly need to learn about digital systems.
What you’ll mainly be dealing with in terms of digital systems are microcontrollers and other embedded systems. I’d say the main two places to get started with those are the Arduino and Raspberry Pi ecosystems. The first is “more pure microcontroller” and the second is “more advanced embedded systems”.
Microcontrollers are mostly programmed in C++ these days (with a few strange people like me using Assembly), and the Arduino ecosystem sort of teaches that. Microcontrollers are usually the most efficient system to make the control electronics for something like a keyboard. Sparkfun and Adafruit are good companies to buy parts to get started from.
Embedded systems like the Raspberry Pi stuff can often run a whole operating system. This is too expensive (power, space, and $) for most keyboard builds, but you may want to learn how to use them for other projects. However, they also make a microcontroller (the Pi Pico) which would be OK and can be programmed in Python.
For advanced computer peripherals, you might need to learn FPGAs. However, that can be a difficult topic to get into by comparison. So maybe leave that for later.
A good way to get started is to buy the parts for, and build, a few Arduino projects. There are specific libraries for making Arduinos emulate a PC keyboard too.
In terms of tools, at first you will just need a breadboard, some resistors, LEDs and jumper wires. Maybe a battery or USB power supply. A multimeter too.
Soon after you will probably want to learn to solder to start making your own standalone devices. You should get a soldering station with temperature control – some people swear by Hakko, myself I have a cheap-but-good Yihua soldering + hot air rework station.
Next, while Sparkfun and Adafruit are great businesses, they are not cost-effective ways to source a lot of parts. You’ll want to learn how to use the part search and ordering functions on Digikey, Mouser, Arrow, and RS Components. Maybe also McMaster-Carr if you do mechanical stuff.
When you have some working designs done, you will probably want to learn KiCAD. It’s software for designing circuits, and laying out printed circuit boards (PCBs) to send to a factory to be made professionally. Through the magic of globalization, this is actually pretty affordable! A typical run costs me 20-40$ for 10 units, and takes 16 business days – although I live in Asia, so it might cost a little more from the USA or Europe.
You’ll also maybe want to learn 3D modelling and printing, for designing cases (I struggle with this more than I’d like to admit). TinkerCAD is an OK place to get started, although tools like SolidWorks are certainly more advanced. You don’t need to buy a 3D printer unless you want to – you can just order your designs made online.
Anyway, the results with KiCAD + 3D printing can be really quite good and can last many years of use. They also let you share your design with others, so other people can make it!
Finally, if there’s a hackerspace / makerspace in your area, these are great communities of people you can learn from. Definitely check them out. They may have a 3D printer you can use, as well as other tools. Often they teach courses too.
One small note – getting from “hey neat this works!” to making and selling a product is (sadly) a really big step. So if you one day want to do that, build a network and ask for advice from someone who has gone through it first.
Man, that was a great read, from simple beginnings to selling your product. Thanks for the thorough explanation, I definitely don’t plan to sell anything, I was considering learning electronics as a hobby, but it’s good to know where to start if it ever comes to that.
Glad to help! I find it quite neat that with effort and time, it’s possible to learn to make quite advanced electronic systems yourself at home. Some of the stuff the more advanced hobbyists make is quite a bit better than a lot of mass-produced goods. We truly live in an age of wonders!
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