Thanks for taking a look! SG is set to 50Ohm output, cable is 50Ohm, terminated “through” 50Ohm at scope end. Also, SG output looks normal on a different scope (same cable/terminator arrangement). Not sure what else I could do to match the impedance here.
Does this scope do Fourier analysis? If so, can you see which frequencies are being suppressed? Does this suppression at this frequency also occur with generated white noise?
Thanks! I tried but I don’t see the effect with noise gen, maybe my measurement is not quite right. Simply punching in a couple of frequencies (60Hz and 200Hz) that I’ve already seen differ in amplitude with the Measure function also has different peak amplitudes in FFT output. Since the frequencies are so low I’ve verified stability of siggen amplitude output with an AC voltmeter and it’s stable within 50uV or so, nowhere near the diff in magnitude measured by the scope. Hmm…
I guess my question to you would be what are your goals? Do you have a project in mind? Do you have a technology, Analog, RF, MCU, FPGA, embedded design? I tend to learn a new thing better when I have an end goal or project to work towards. Depending on where your starting from, a pi might be a good place to start too. You still have most of the I/O and busses of an Arduino, but you can program everything in python, and you have the resources of a full OS too.
Probably stuff like microcontrollers/embedded applications! (I’d like to think) I already know much of the higher-level concepts of computers and how they work, I’ve messed around with programming in Rust or C#, I’ve been daily-driving linux for a few years, I’ve wrote software to do basic tasks for me, but my end goal is to apply my experiences to the physical world. I know very little about the basics of electronics, the physics of it, why PCBs are designed the way they are, etc.
I guess I’d like resources for the lowest-of-the-low-level stuff? Like “How electricity in general works”, “Use-cases for resistors”, “Why you sometimes see capacitors in weird places”, etc.
I’m just now realizing how vague my original question was? i’m sorry about that haha.
I don’t have a particular goal in mind though, i just think this stuff is cool, and I’d like to at some point be able to sit down and make something wacky or useful with KiCad/similar.
I’ll start off with your questions are a outside of what I know well. In general to do stuff with electronics, you don’t need to know the physics behind it, but the equations that pop out. Mainly V=IR, Almost everything goes back to that. Behind the scenes are lots and lots and lots of differential equations. Alpha Pheonix has a few good visualizations for resistance. He has a water based demo to visualize voltage and resistance, and a maze demo showing how electricity “finds” the path of least resistance. ElectroBoom probably won’t teach you too much, but can show some interesting things you can do. EEVblog has some good lectures. For specific applications Digikey and Texas Instruments have some basics, and there are many lectures online available.
I think the questions you asked are a little more on the physics side than the electrical side, and the specifics I think of as a dark art that comes with experience. In general most capacitors you see are blocking DC on an AC circuit, coupling capacitors that are smoothing the power circuit, or capacitors to control/tune something specific. Those control values would be given in a datasheet. Resistors are often going to be current limiting, voltage dividing, or “pulling” a high impedance signal. To design something you often just need the rule of thumb, and not necessarily a deep understanding of “why”.
Based on the experience I gathered in repair cafes:
Some old power switches generate an arc (spark?) when flipping them. Cleaning their insides with an "electrical contact cleaner" spray can sometimes help.
Defective electrochemical capacitors do NOT always swell or leak. If it is worth it swap them all for new ones (We sometimes desolder what we think are good ones from dead appliances to be re-used).
All domestic appliances around here (France) have an "anti surge" (?) capacitor soldered just after the power cable and power switch. If I understand it correctly, its job is to prevent a "parasitic" current spike to travel back on the domestic electric network when the equipment is switched on. That's the one I would replace in priority to see if it fixes your problem.
Disclaimer : I have no degree in electronics / electrical installations. Take what is above with a grain a salt as I might be dead wrong.
Always unplug the appliance from the mains before tinkering and discharge ALL the capacitors which are on the 110 V /220 V side of the electronics before touching the PCB on which they are soldered.
Good luck with your repair. It would be nice and helpful if you have a chance to post some pictures :)
To fool the computer into not throwing an airbag light and disabling all the airbags. I have an early 00s car that swings double duty as street car and track car and when I pull the driver’s seat out for a race seat, the airbag light shows up. Then I go through a rigamarole to reset the light once everything is swapped and plugged in again. It’s a common mod, but just people usually cut up the harness. I’d like to keep things neat and tidy so I bought the seat side of the harness and want to cut the plug off, solder on the resistor and plug it in.
Do you have a datasheet/part number for the LEDs, or at least a picture and diameter?
Because battery voltage reduces over time, the LEDs will get dimmer as the battery drains fairly quickly. If possible, running it off a mains plugpack (e.g.12V like for a router or external hard drive) would be good.
An example UV LED has a forward voltage of nominally 3.7V. Two in series on a 12 (8x1.5V) supply gives us 12V-(2x3.7V) =4.6V to drop across the resistor. We want ~15mA, so need a very roughly (V/I =R) 4.6V/0.015A=300 ohm resistor.
When the battery is nearly discharged, at 1.1V/cell it will be 8.8V, giving 1.4V across the resistor and V/R=I 1.4V/300ohm= 4.7mA.
So you would connect each pair of LEDs as:
BAT+ RES +LED- +LED- -BAT all in series. Like this.
You’ll need another 10 300 ohm resistors for 15 total, one per pair of LEDs.
You could connect the LEDs in 5 strings of 6 parallel LEDs, each string with it’s own 100 ohm resistor. You will need a significant amount of voltage for that, at lest 7x the threshold voltage of the LEDs
AA batteries can supply plenty current, the question is for how long.
You need about 1.3 Watt for 30 LEDs (I’m assuming 15 mA, 3V). A rechargable AA battery has about 2.4 Wh according to Wikipedia, so 6 AA batteries will last you 2.4Wh * 6 / 1.3W = 11 hours.
I have no idea how curing works, but 1.3 Watt feels very low. That amount of power is fine for visual lighting, or for signals (turn on a TV), but energy wise it’s very little.
I had something similar happen in one of my ESP8266 projects (also running MicroPython). What I wound up doing was, every five wall clock minutes (maybe a bit sooner than that, for your case) I had my firmware do a local_networks = wifi.scan() just to exercise the wifi functionality. If that failed I have the code do gc.collect() followed by sys.exit(1), which causes the 8266 to reboot automatically.
Do you have any idea, what’s causing the issue? Is it specifically the scanning part that’s relevant here? I’m starting/stopping wifi each minute, so the chip shouldn’t just idle around all the time.
No, I don’t. My best informed guess is that the wifi connection’s state machine gets stuck once in a while, it misses a couple of packets, and then sits there doing nothing. So, by kicking it a little it doesn’t get a chance to freeze up.
I “kind of” solved at least parts of the problem by simply not turning wifi off. It’s more stable than before, but not stable as such.
Edit: I played around a bit and I think the problem is somewhere in the power supply. My workbench PC can drive the board just fine for hours, just plug it into the USB port, connect serial monitor and let it do its thing. However, if I’m plugging it into my router or a usb power supply, it stops working after a while again.
My theory is, that the PSU/router thinks the device is dead, because it draws too little power? That would explain, why not shutting down wifi improves the stability - it draws more power.
Now, that is just my naive theory, I’m not entirely sure, how to validate it. Maybe I’ll just add a useless busy-loop to increase power draw or add some power consuming components.
Easy, you import this puppy www.ebay.com/itm/305042665748 and set up your own business offering calibration services to recoup the cost. Then you can apply for the calibration engineer position at Minerva.
Jokes aside, have you contacted a calibration lab? I don’t know what it’s going to cost, but I can’t think of another way, if you’re not going to built the sources yourself. There’s one in the Netherlands www.minerva-calibration.com/calibration-service/
It would seem from a quick google that I’m not alone in my conclusion. But at least I have found an article explaining the build of the sources you need wolfalex.bplaced.net/…/calibrator.htm
Their pricing for calibrating a device starts at around €400, which is rather more than I paid for this thing and way more expensive than building my own calibrator. So I guess I’ll have to do that…
(…) I have found an article explaining the build of the sources you need
Thank you! Not having to invent everything from scratch is going to make this a lot easier.
400? I guess that’s in the ballpark I expected it to be.
I haven’t studied the BOM for the DIY solution, but something tells me that you’ll only be able to keep the cost lower than 400, if you value your time at close to zero.
With all that negativity out of the way, I’d definitely want to build it myself too. Although my anxiety level is exponentially correlated to the working DC voltage and at 300VDC I’m definitely well in the thick rubbergloves territory. Be careful with the build!
my anxiety level is exponentially correlated to the working DC voltage and at 300VDC I’m definitely well in the thick rubbergloves territory.
Having been walloped by 230VAC, which is far more dangerous, I’m not too worried.
Looking at the schematic you linked above, the amperage is going to be low, which is reassuring. As a safety measure, I’m looking into running the thing off of a battery, so that if the worst comes to pass it simply won’t have the power to be dangerous (1A at 12V translates to a mere 40mA at 300V).
I’d be far more worried about using lead solder TBH (love my Sn100Ni+).
Having been walloped by 230VAC, which is far more dangerous, I’m not too worried.
Well hello there Mr Edison, I didn’t realize the calendar read the 1880s again, please refrain from elephant ownership 😀 First off if you’ve got 300V I don’t care what form it’s in, I ain’t sticking my fingers anywhere near it! Secondly at least AC alternates, giving your muscles a break and possibly a chance to let go of the wire, DC isn’t that forgiving. The reason 230V AC is so dangerous is because it’s usually referenced to ground, meaning that if you touch a single wire, you’ll be drawing a current from that point and to your feet.
But that is all theoretical, because while 300V is stored, and the current may become quite high, it’s only backed by 100nF. Still, I’d want it discharged before poking about though.
The battery is a good precaution. Some of my co-students in university made an EKG apparatus. Our lecturer demanded that anything connected to the electrodes was to be powered by a single battery.
I’d be far more worried about using lead solder TBH (love my Sn100Ni+).
I may be a boomer in this regard, and I’m sorry for the rant I’m about to go on (that last part of the sentence was tagged on after writing the following). I prefer my Sn60Pb40 of which I got several kg from when it was outlawed, maybe throw in a little Ag in there for the 0.3mm SMD solder. TBH my love of lead solder may stem from the fact that I have more, in various diameters, than I’ll ever use.
The first couple of lead free solder brands I got just didn’t flow right. It didn’t help that the solder stations it was to be used with at work, by students, was old school Weller stations that just delivers a constant 24V AC to the iron, and the tips set the temp. All the tips we had were at a temp comfortable for lead solder.
Secondly at least AC alternates, giving your muscles a break and possibly a chance to let go of the wire, DC isn’t that forgiving.
Interesting. Your comment made me read up on all of this. Note that, since Vrms = 1 ÷ √2 × Vpeak, 230VAC has a Vpeak of 325V, so in that respect, it should be pretty much equivalent to 300VDC. I figured that the ability for AC to induce heart fibrillations was the most dangerous factor in all of this, but I hadn’t figured in that DC induces tetanus and can also temporarily stop the heart.
It’s not the volts that kill you though, it’s the amps (the volts just make it easier). I found a table listing the effects of various amperages. It does present DC as generally more safe when compared against 60Hz AC, but I’m not sure how that generalises to the 50Hz AC we have here. I do conclude however that I should be limiting the output current to something something generally safe, like 20mA (which should be fine for a voltage reference). I’m thinking a PTC at the input and being conservative wrt capacitor sizing should do it.
Some of my co-students in university made an EKG apparatus. Our lecturer demanded that anything connected to the electrodes was to be powered by a single battery.
TBH, when it comes to an EKG apparatus I’d also be worried about common mode across the chest, or the power supply having a disastrous failure mode.
I prefer my Sn60Pb40 (…) The first couple of lead free solder brands I got just didn’t flow right.
Yeah, those were horrid. Even the supposedly excellent SAC305 gave me dull joints (tough it flowed adequately). Still, I can only recommend Sn100Ni+ (supposedly closely related to SN100C): flows well and gives me the shiny joints I crave. Having a good soldering iron (I’m using a Pinecil) helps with solderability.
I do however still have some rosin core Sn60Pb40 for reworking vintage electronics. And I do agree that it’s just better when it comes to wetting ability. The peace of mind when working with lead-free solder really is worth it though, especially with pets or small children.
The device is supposedly a 6½ digit DMM yet I currently don’t even trust the first few digits when comparing it to a 3½ digit handheld Brymen DMM. Being reasonably sure that it’s at least more accurate than the Brymen would be nice, so 3½ digits.
I’ve got another desktop DMM, a 5½ digit GW Instek GDM-8255A, on the way, so I could conceivably just use that one as my local “standard” to calibrate against.
The problem however is that the Philips requires a large amount of references to calibrate against (just calibrating DC voltage requires 0V, 3V, 30V and 300V references). Building all references to recalibrate the whole thing would be rather involved, so I was trying to find an easier way.
You want to put the batteries in parallel, so you’ll have double the capacity. Installing them in a series would increase voltage and most likely damage something (mixing 12V systems with 24V battery pack doesn’t really work). Increasing capacity with another battery can cause strain on charger components, so make sure they’re beefy enough or at least have proper protection against overcurrent.
People are correct that you should use the same capacity batteries, preferably the same make/model and age. Mixing batteries can cause problems where one battery drains faster and other(s) start to charge the lower level one so you’ll have less useful amp-hours and that degrades batteries faster.
Switching batteries with a relay or a switch is possible, but you need quite big and good quality relays/contactors for that as current can be pretty high which can cause arcing and even weld contacts together eventually. With proper parts it’s a safe way of doing it, but personally I’d just get two batteries in parallel since there’s fewer components to malfunction and adding complexity with arduino+contactor doesn’t save that much money, specially if you place any value for your time (which of course isn’t necessary, tinkering itself is often worth the time spent).
The issue is that I cant place two of the same batteries. The extra one has to go under the passenger chair so it will be a completely different battery. I’m not completely sure that we won’t be running into issues then when linked in parallel.
I agree that the relay option it’s added complexity and finding the right relay is a bit of a challenge haha. Also there probably will be a short drop in voltage or I have to switch them shortly after each other. So both relays are closed at the same time for a little bit. I don’t know if that would fix the arcing? It will be linked in parallel for a little bit then I guess.
Get a switching relay or one normally closed and another normally open one. That way there’s no paraller connection at all. Connecting two batteries together with different voltage levels causes a huge current spike, think jump starting a car and how thick those cables are. Arcing will happen on the relay contacts no matter how you switch it if there’s load connected.
And since you’re not talking about a trailer, is one of the batteries for the car itself? Since if you’re planning to use the secondary battery as a car battery too you need very heavy wiring to give starter enough amps to run plus running that over a relay is a whole another beast to manage since starter motor can pull hundreds of amps momentarily.
Is an extra utility battery. So that shouldn’t give any issues for starting. That’s a separate battery. I’ll try to find one of those relays. I know I can search myself but if you have any suggestions they are always welcome:)
So you’ll have total of 3 batteries at the car? One for engine, existing utility battery and now you’re planning to install another utility battery, right? That should work. I don’t know how much current you’re pulling from the battery, so it’s difficult to recommend anything. Common bosh switching relay is something you can find from pretty much every car part store for ~5€, but I think they’re rated only up to 40A and I wouldn’t push them to the limit. Check your inverter datasheet how much current it can draw and preferably get a relay which can do double the maximum rating for longevity and stability.
That is correct. 1 battery for the engine and 2 for utility. I guess it has to be quite a beefy one. The interter is rated for max 166 amps. So that’s quite a bit. Which also makes it a bit hard to find a suitable relay.
12V 200A relays are pretty easy to find (I wouldn’t get one from alibaba tho), but that much current requires quite beefy wiring as well. Personally I’d review options to place auxiliary batteries in parallel since that would simplify wiring and the whole system a bit, but as I don’t know how your camper is built it can be tricky or you need to sacrifice storage space somewhere.
And as you’re placing a battery at the same space where people stay be careful with hydrogen. Charging lead acid battery produces hydrogen and in the worst case scenario, specially if you have a gas stove be dangerous if not lethal.
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.
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