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kid sinister posted:Define "cheap". How much are you looking to spend? Ideally sub $500 and bonus points if it's not physically large.
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Apr 3, 2024 01:38
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TwoDice posted:Ideally sub $500 and bonus points if it's not physically large. I use both https://www.amazon.com/gp/product/B0771N1ZF9/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&th=1 and https://www.amazon.com/gp/product/B07PWZTNJK/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1 and have been basically happy with both. The handheld one is very basic in term of features and capabilities but it's good enough for basic diagnosis when I can't be bothered to carry something over to the real scope.
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Apr 3, 2024 01:47
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I like my Rigol DHO914 but in retrospect I wish I had bought one of the N-1 scopes without a touchscreen interface. Maybe I'm just so used to 20+ years of occasional scope usage that flipping options with a knob doesn't bother me at all, while poking at a screen with a sausage feels clunky. I think with the DHOs being the new "hot" thing I'd see if the N-1 scopes are going on discount. I doubt they're worth turning a nose up at, especially if the DHO is at a 4-500 price point. I went with the 914 strictly because I wanted to future-proof with the ability to use it as a logic analyzer as well, only the OEM probes cost as much as a base DHO itself, and are way way way more expensive than a bespoke USB logic analyzer which would probably be more versatile anyway. There's a handful of DIY probe projects listed on eevblog forums that I'm going to look into, but part of me is just thinking of going the buy-once-cry-once route on the OEM probes. I'd have to hand assemble that DIY solution for probably a hundred bucks anyway, and would almost certainly botch it at some level. some kinda jackal fucked around with this message at 11:57 on Apr 3, 2024 |
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Apr 3, 2024 01:50
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I've been happy with my vintage CRT scope, it's main limitation is that it's only 40mhz, but it's been an issue only a few times.
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Apr 3, 2024 05:18
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I ended up ordering an sds804x, we'll see how it goes. (https://siglentna.com/digital-oscilloscopes/sds800x-hd-digital-storage-oscilloscope/ )
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Apr 3, 2024 13:07
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Weren't there some Siglent scopes you could hack for more capabilities too? Might be worth checking out. I only have a $60 aliexpress scope so I'll never know 
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Apr 3, 2024 21:20
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I don't know about Siglent, but the Rigol 1054z was so trivial to hack that they just ship will all the features unlocked now.
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Apr 3, 2024 21:41
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lmfao holy gently caress how did I go this long without a pair of magnifying goggles for soldering?? It turns out being able to clearly see what you're doing makes soldering much easier. Controversial take, I know.
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Apr 4, 2024 00:33
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some kinda jackal posted:lmfao holy gently caress how did I go this long without a pair of magnifying goggles for soldering?? I got 20/13 vision. Never saw the need for them. Then I turned 40... I should pick up a pair. My eyes don't focus as fast as they used to. Switching from my phone to the TV takes awhile. kid sinister fucked around with this message at 01:25 on Apr 4, 2024 |
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Apr 4, 2024 01:23
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This is the year my eyes started to go and I've been low key crushed by it. I finally decided soldering a lipo battery to a board without shorting something and setting my house on fire was a bridge too far and bit the bullet. Literally wish I'd done this years ago even if I didn't need it.
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Apr 4, 2024 02:47
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I gotta say, for dealing with vacuum tubes as often as I do, I'm glad just how reliable they are decades later. I mean, they have sockets for quick exchanges, but I rarely need such convenience. In fact, now that I think about it, I've probably had more problems with the sockets than the tubes that go in them. Now if only capacitors were that reliable... You young kids should be glad we don't use paper wax caps anymore. They're sticky and gross!
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Apr 6, 2024 16:22
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some kinda jackal posted:This is the year my eyes started to go and I've been low key crushed by it. I finally decided soldering a lipo battery to a board without shorting something and setting my house on fire was a bridge too far and bit the bullet. Literally wish I'd done this years ago even if I didn't need it. Trying to shift focus close up like that started giving me headaches in my 30's, so I picked up one of the Hayear hdmi scopes and some barlow lenses for it so I can mount it up high, I love it so much. It's great for getting slivers and poo poo out too. Not having to crouch over to look at it with the goggles is nice too. I don't really miss the 3D depth perception either, I know that bothers some people but I have not found it to be a problem when soldering.
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Apr 6, 2024 18:10
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kid sinister posted:Now if only capacitors were that reliable... You young kids should be glad we don't use paper wax caps anymore. They're sticky and gross! Isn't there a kind of generational variation in the quality of capacitors? I remember it being a common enough this in the very late 90's into the early 2000's to have to resolder all the caps on a motherboard because they'd all swell and burst. That apparently resolved itself at some point?
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Apr 6, 2024 18:22
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Rocko Bonaparte posted:Isn't there a kind of generational variation in the quality of capacitors? I remember it being a common enough this in the very late 90's into the early 2000's to have to resolder all the caps on a motherboard because they'd all swell and burst. That apparently resolved itself at some point? It was a whole thing https://en.wikipedia.org/wiki/Capacitor_plague
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Apr 6, 2024 18:29
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Rocko Bonaparte posted:Isn't there a kind of generational variation in the quality of capacitors? I remember it being a common enough this in the very late 90's into the early 2000's to have to resolder all the caps on a motherboard because they'd all swell and burst. That apparently resolved itself at some point? That was electrolytic caps about 20 years ago. It was the result of corporate espionage stealing only half the formula. It's been a thing among several lines of caps over the decades. For instance, Adrian Black on YouTube restores old Mac computers. Those 40 year old computers have Vera branded caps that are known to go bad. We are also reaching the age in other electronics where the caps started failing. Sega consoles and peripherals from the 90s have begun having their electrolytics go bad.
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Apr 6, 2024 18:40
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I've been looking for a 4-bit level shifter to tap into my car wiring, so I need something that would do ~12v -> 3.3v (one way) Looking at TI's stuf here though it seems the only option is CD4x like CD40109B here https://www.ti.com/lit/ds/symlink/cd40109b-q1.pdf but they all seem to be low-to-high: quote:CD40109B contains four low-to-high-voltage level-shifting circuits. Each circuit will shift a low-voltage digital-logic input signal (A, B, C, D) with logical 1 = VCC and logical 0 = VSS to a high-voltage output signal (E, F, G, H) with logical 1 = VDD and logical 0 = VSS. So the 18v models are low-to-high, and all other options seem to only go to 5.5v. Am I missing something here? I only really need to measure pulse widths at relatively low frequencies (~100Hz) and the different signals don't need to be perfectly timed together. Could I just get away with using voltage dividers here? mobby_6kl fucked around with this message at 14:46 on Apr 7, 2024 |
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Apr 7, 2024 14:43
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mobby_6kl posted:Could I just get away with using voltage dividers here? John Peatman (professor, prolific writer in the EE trade/hobby press) did this trick for talking to 5v ICs with the PC serial port (+/- 12V typically) where his level shifter was just a big (I think like 100k) resistor between the serial port and the pin. This "worked" because the protection diodes in the IC would take the hundred or so μA and clamp the voltage to near the supply and ground. Whether that really works depends on the type of IC, whether it causes you to violate any datasheet limits, whether you care if you violate those datasheet limits, etc. That's the bare minimum for level shifting down. A voltage divider is downright fancy by comparison. If you want to get into premium territory, replace the bottom resistor with a small signal schottky diode from the power supply (as in, pointing from your 3V supply to your logic level pins) and you're safe even if you have an unexpected voltage spike on the input.
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Apr 7, 2024 16:03
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Stack Machine posted:John Peatman (professor, prolific writer in the EE trade/hobby press) did this trick for talking to 5v ICs with the PC serial port (+/- 12V typically) where his level shifter was just a big (I think like 100k) resistor between the serial port and the pin. This "worked" because the protection diodes in the IC would take the hundred or so μA and clamp the voltage to near the supply and ground. Whether that really works depends on the type of IC, whether it causes you to violate any datasheet limits, whether you care if you violate those datasheet limits, etc. I've found that sometimes the datasheet of a part (or if it's a part made by multiple suppliers one of the datasheets) explicitly calls this out as possible in a little note or something, like "if current is clamped below [value] the device can be driven higher than Vcc". I've definitely done that in a few designs myself where the datasheet explicitly said it was ok (too much of a coward to try it otherwise ) and it Just Worked.
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Apr 7, 2024 16:40
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Yeah no doubt that a voltage divider will "just work" but it's weird that this situation doesn't seem to be well covered. I did eventually found https://www.nexperia.com/products/analog-logic-ics/voltage-translators-level-shifters/74HC4050D.html which claims quote:The 74HC4050 is a hex buffer with over-voltage tolerant inputs. Inputs are overvoltage tolerant to 15 V which enables the device to be used in HIGH-to-LOW level shifting applications. It's too large though so unless there's a 4-channel version, I might try that diode suggestion. The main priority is not blowing up the ECU 
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Apr 7, 2024 20:50
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Is this for data or power? If it is for data, I would just get some MOS transistors where you have your logic voltage sitting on one end and set up a resistor network that lets you use the 12V on the gate of the transistor to activate it.
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Apr 7, 2024 20:53
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Car power is gross and nasty, so use an optoisolator. Car power can have spikes of -20 to +80V for hundreds of milliseconds.
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Apr 8, 2024 01:44
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ryanrs posted:Car power is gross and nasty, so use an optoisolator. Car power can have spikes of -20 to +80V for hundreds of milliseconds. +1 for grossness. Now alternators do have a regulator, but it's more of a suggestion and it is meant to recharge the battery. The car's electronics are more of an afterthought. They will in turn have their own silicone covered and weather sealed regulators to run their delicate ICs and such.
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Apr 8, 2024 01:50
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ryanrs posted:Car power is gross and nasty, so use an optoisolator. Car power can have spikes of -20 to +80V for hundreds of milliseconds. Say the spikes were 10x worse than this, like 1kV. If the resistance into your clamp/divider is 100k, your clamp (or the IC pin) has to briefly handle 10mA. The optoisolator will work of course but it seems like overkill, especially if your power supply isn't isolated. (If your power supply is isolated an optoisolator is basically required.)
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Apr 8, 2024 03:35
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Car power is dirty, but if this is for data coming off sensors in the car or something, wouldn't their power have been regulated before hand? I doubt they are building the ECUs to withstand 80V on the data pins.
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Apr 8, 2024 05:45
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I'm surprised cars aren't just constantly frying themselves.
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Apr 8, 2024 08:10
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The "+12V" from the alternator is indeed kind of nuts (and actually >14) but this is for data coming out of the ECU which seems to be stabilized at 12.4 or so. I looked at it on the scope and it seemed pretty clean and if it's spiking over 1kV I probably have bigger problems 
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Apr 8, 2024 12:43
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Cojawfee posted:Car power is dirty, but if this is for data coming off sensors in the car or something, wouldn't their power have been regulated before hand? I doubt they are building the ECUs to withstand 80V on the data pins. Most sensors are fed from the ECU, which will have its own regulated supply. You'd be looking at about 11 to 15 volts supply, though the pots in some sensors will bring in low voltage depending on their position. Rocko Bonaparte posted:I'm surprised cars aren't just constantly frying themselves. Some do! That was actually a recall on my F250 about 20 years ago. The brake sensor going to the cruise control could spontaneously combust, even when the car was off and parked! There was a recent recall for Kias made about 10 years ago for a very similar problem, flames and all. kid sinister fucked around with this message at 16:39 on Apr 8, 2024 |
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Apr 8, 2024 16:22
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mobby_6kl posted:The "+12V" from the alternator is indeed kind of nuts (and actually >14) but this is for data coming out of the ECU which seems to be stabilized at 12.4 or so. I looked at it on the scope and it seemed pretty clean and if it's spiking over 1kV I probably have bigger problems 1 farad cap on the alternator, not cause you have a booming system but just as a low pass filter
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Apr 9, 2024 03:16
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CarForumPoster posted:1 farad cap on the alternator, not cause you have a booming system but just as a low pass filter The only use of a cap that large for a consumer that I can think of.
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Apr 13, 2024 01:06
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kid sinister posted:The only use of a cap that large for a consumer that I can think of. Supercaps are very useful in lots of consumer stuff but not counting those, yeah sure.
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Apr 13, 2024 01:18
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Shame Boy posted:Supercaps are very useful in lots of consumer stuff but not counting those, yeah sure. Interesting. Such as?
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Apr 13, 2024 01:30
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Battery replacement
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Apr 13, 2024 01:34
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Speaking of cars, that's where I've seen super caps being used as replacements. It seems they wouldn't have the lifetime of a battery though.
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Apr 13, 2024 01:49
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There's little toy cars that just have a tiny motor and a supercap in them and so you can charge them up real fast. They only last maybe a minute, but you can charge em' so fast it's fine. Those are pretty fun. Other than that, they're used instead of batteries for keeping RTC's / SRAM going during power interruptions. I've designed stuff that used em' that way even.
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Apr 13, 2024 04:46
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kid sinister posted:Speaking of cars, that's where I've seen super caps being used as replacements. It seems they wouldn't have the lifetime of a battery though. Actually seen them being used?
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Apr 13, 2024 05:08
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ryanrs posted:Actually seen them being used? The original Xbox was famous for using a supercap (2.5V 1.0F) instead of a battery for running the RTC when there's no mains voltage. Unfortunately, they used stupidly cheap ones that were prone to leaking, and the electrolyte on aerogel supercaps is a strong base and will easily eat through nearby traces on the motherboard. One of the first things you do when restoring an OG Xbox is remove it. (Reverse engineers suspect that it was a cost-saving thing -- they integrated an RTC into the southbridge, instead of having a standalone RTC chip on the board. They later realized that their design required them to power on the entire southbridge chip in order to run the RTC, and that it would drain any coin cell in a matter of weeks, meaning it'd be dead by the time it got shipped to stores and sold to an end user. Hence, the supercap as a fudge.)
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Apr 13, 2024 05:30
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I would think some supercapacitors would be good for "smoothing" battery use in long-term things with weird behaviors, like if you have solar panels and a battery inverter thing and you have something connected to it that uses *about* the same amount of power as the panels produce, instead of constantly charging and discharging the battery a little bit you could do that rapid-cycling in a capacitor instead, which would be an improvement for the battery's long-term lifespan? Or is batteries' lifespan being measured in cycles misleading? Or do capacitors also have a limited number of cycles?
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Apr 13, 2024 05:33
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I would also have accepted "We used a supercap to avoid scary lithium battery shipping labels". e: 5.5mAh coin cell weighs 0.23 grams and restricts your Digi-key order to ground shipping only. 
ryanrs fucked around with this message at 05:40 on Apr 13, 2024 |
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Apr 13, 2024 05:34
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ryanrs posted:I would also have accepted "We used a supercap to avoid scary lithium battery shipping labels". That’d be a good excuse today! Xbox was a 2001 product though, IATA shipping regs started in 2008. Bunnie measured the current on that supercap, and it was 140uA to maintain the RTC in the southbridge, which is absolutely nuts. A dedicated RTC is 200-400 nA.
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Apr 13, 2024 06:26
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Ha ha, for 140uA I feel like you could run a power optimized 32-bit ARM core (like a Cortex-M0 or M4) at 1-5 MHz.
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Apr 13, 2024 06:57
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