I work with a lot of particle detectors. Instead of this, I recommend a photo diode and laser diode. Light dispersal particle counting is relatively easy to pull off by comparison to scraping off coating and all that. You could even use a very small segment of solar panel and a light source or an IR detector and IR LED similar to a smoke detector.
I recommend EEVBlog’s OpAmp tutorial. His explanation is pretty simple to understand. Basically there are two rules (note these rules are ideal, but the exceptions can usually be ignored):
No current flows into the inverting and non-inverting inputs.
For negative and positive feedback circuits, the OpAmp wants to keep the inputs the same by changing its output, and will sink power to its positive or negative power rails to achieve this.
Buy the JST plug with the right pin pitch (in your case 2mm), and grind it so it fits. You can find male to female cables, so you also don’t have to modify the original connector on your noctua fan.
Play memory or with a wooden kitchen. I’d say 3 is too young. you can get some basic electronics kits for children. just visit one of the toy stores. But playing with electronics and doing experiments starts being fun at around 5 to 8 years. Maybe playing with an extension cord at 4. but you wouldn’t want to encourage a little kid to play with extension cords, plugs and mains power…
Don’t worry, we’re already doing all the typical toddler games and I’m not keen on raising a STEM child prodigy. That’s why I asked for hands-on experiences with prodcuts specifically for toddlers.
Alright. I think i misread things and thought you were after an (strictly) educational kit. Just wanted to say that. We gifted an (quite comprehensive) electronics kit to a seven year old and that seems to be a good age to start. but under 5 i can’t see a kid having the attention span, dexterity or mental abilities to grasp concepts aside from on/off, this is a light and this is a switch. but i may be wrong. there is certainly no harm in starting too early. i just think it wont be fun or of value for a 3 or 4 year old. in my experience they get bored quickly if you try and convey theoretical concepts. at that age i see kids playing with wooden tools, train their dexterity with a small hammer and nails game. or mimick their parents and play something like cooking or doing the dishes, that has something to do with their every day life. nonetheless. try it. i’ll bookmark this and read all the ideas and experiences of other people. maybe i’m completely wrong. one thing i observed kids are interested in all kinds of silly stuff. and they start asking questions as soon as they can. and i believe it is a good thing to encourage them in asking questions and figuring out concepts and how things (including physics) work.
edit: some dads build a big wooden box with (old) sturdy buttons, switches, indicator lamps, a vandalism-proof keypad, etc for their toddlers. i saw a few blog posts years ago. But that was completely DIY. I don’t think it teaches anything but dexterity, but toddlers like pressing buttons. And it’s a cool project. And a few years later you can use it as the main console for your imaginary space ship. ( youtube.com/watch?v=j6zseFi070E )
Get them working on their mathematic skills, instead. You can give them a really good head start - mine could solve simple differential equations at age 11.
The oscillator is creating both DC and AC. The DC component is the average value of the signal. In the case of your 0-10v square wave, that is 5v. The AC compnent is the part of the signal that changes. The effect of the capacitor is to block the DC component, leaving only the AC component. The waveform is shifted vertically to be centered around 0v.
In my opinion an oscillator always produces an AC sine wave. There is usually no need for a DC overlapped oscillator signal. The DC supply of an oscillator produces a AC sine wave relative to GND.
Where exactly did you measure a DC sine wave, relative to what, and what do you mean by “AC removes a DC component”?
Assuming that the ribbon cable is standard - you could consider adding TWO IDC connectors, side by side. Then slice the cable through between them. Then add a standard extension cable to link the two. Indeed if one of the two is male, the other female - the extension can be removed if the thing is relocated to where the extension isn’t needed - or a longer one is needed.
I confess to having done this sort of mod several times, myself. It’s also quite an easy way of sticking a protocol analyser/sniffer between the two and/or modifying the data that is sent on its way. Or adding an additional sensor (even of a different type) and converting its output to something suitable.
That sounds… Difficult :p I really don’t want to slice anything to void warranty and such. I’ve been spending a lot of time trying to look for some sort of extension cord or connectors so I can make my own, but I was wondering… can I just use this? www.amazon.nl/…/B01EV70C78/ Would be so much easier 🤔
Lots of people use them for something similar. Obviously, the situation changes once the lines are power lines and not signal lines. If you can stabilise the result and add strain relief.
The diodes at least provide some steps - which just LEDs and resistors don’t. The dissipation in the main series resistors will be quite something, also. (You will probably need several resistors in series, if you use standard ones, with their standard voltage limits).
I’m assuming that those "v"s are meters and not constant voltage sources. A 2.4v zener does NOT have exactly 2.4v across it. A 1.2 v supply will not be precisely 1.2v. Both will also vary with time and temperature. So, in practice there WILL be a dc component across the sensor - which will destroy it.
Thank you. Do you recommend me something (circuit) else? The 2.4v zener would provide about 2.4v. To keep 1.2V exactly half of the zener produced by the zener, I was considering split its voltage with 2 x 10k resistor in series and feed into an opamp in buffer configuration, so even it the 2.4 reference changes a little bit, the other side of circuit would be always zener / 2.
How I would do it is to use two digital IO pins on the processor to generate the reference square wave. Put the sensor plus a series precision resistor between them and just pull one IO pin high as the other is pulled low and then swap them. That presumes that IO pins can both source and sink IO current. Then take the junction between the two to an Analogue in pin. You get two measurements each cycle. Use a lookup table of values and interpolate between them. If you wanted more precision - add more series resistors of different values covering the range of humidity that you want to sense, going to different IO pins. So you can choose the IO pin pair that brings the centre point between sensor and resistor closest to the mid-voltage point. It’s effectively a balanced half bridge arrangement - using the precision of the resistors to determine overall measurement precision. OK it ties up several IO pins - but microcontrollers are so cheap, I’d probably just dedicate one to this sensor and that’s all that it would do.
...but how in the world do you burn a 1 GΩ resistor? That looks sort of like it could be a 1 watt resistor too. So back-of-the-napkin this would have to be from over a 30kV supply. So that sounds a bit off.
Unless it isn't. One hell of a bread maker then. I want one.
Only thing I can think of, maybe it’s a bleeder resistor for that cap, and it failed by some kind of internal short which reduced its resistance (and increased its heat dissipation hence the blackened board)? But fails-short is an unusual failure mode for a resistor and 1 GΩ is pretty high even for a bleeder, so maybe we’re misreading something.
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