The standard way of looking at this is to consider a capacitor-resistor series combination going to ground. Connect a 10v (wrt ground) supply to the capacitor and the voltage across the resistor rises to +10v, then decays. Now connect that capacitor to ground and that same resistor gets -10v across it, which then decays. Whatever is connected to the capacitor “top” terminal has to be able to sink current as well as source it.
That’s what generators in simulators do - they have zero internal impedance (usually). They sink currents as well as source them.
See if you can swap the connector, those pins can be released if you gently lift the locking tabs and pull the wire away from the connector. The metal connectors from your replacement fan might not fit into the original, but it’s worth a try.
Thanks for this suggestion! Is there any chance of breaking the connector by doing this? I replied to another commenter, but to emphasize, I am only looking to modify the fan and connector as a last resort because of how rare this equipment is.
Breaking the plastic would be tough so long as you’re not hammering it. The connectors crimped to the wires it’s another issue and if you pull too hard you could get the wire to come off the connector if it isn’t soldered.
Yes you could break the connector if you’re not careful. However at the end of the day, it’s not like you can’t replace both sides of the connector with standard hardware, and at the very worst you could solder the fan to the pins and cover each wire with heat shrink.
That’s why they call it a decoupling capacitor, cuz you usually just need AC (signal) at the out of a circuit, you don’t need the DC part of the signal.
True AC is sort of “balanced” in that it has just as much positive as negative. The positive area of the waveform is the same size as the negative area. For waveforms that are sort of symmetric across the 0V with a time offset, such as a sine or square wave, this means that it is centered along the 0V line. A DC source, on the other hand, never changes voltage.
The 0V to +10V source you have is actually a -5V to +5V square AC plus a +5V DC. The capacitor is getting rid of the DC component leaving just the AC, which happens to be the -5V to +5V AC that you are getting.
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”?
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.
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.
I think that it is the same stuff, just will propellant added in the aerosol. A small squeezy bottle with a needle is better if you have live stuff nearby - but you can always fill one from an aerosol
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