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Test Equipment / Re: SDS800X HD Actual Use Cases
« Last post by Njk on Today at 01:32:03 pm »BTW that use case shows that a floating scope can't be always substituted with an isolating transformer.
Recent Posts
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Metrology / Re: ADR1001 - Ovenized Voltage Reference System
« Last post by picburner on Today at 01:31:00 pm »It says July 3rd to me.... and date approximate an subject to change.....
Will we talk about it again for 2025?
Will we talk about it again for 2025?
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Microcontrollers / Re: Attiny1606 burning out when connected to a drv8251
« Last post by pcprogrammer on Today at 01:30:29 pm »Your Attiny might need better power supply decoupling. In the schematic there is only a 10uF capacitor to decouple the Attiny, and it might be that internal oscillations cause it to overheat. Try adding a 100nF capacitor as close as possible to the Attiny power pin.
Another problem can be when the motor starts to run due to the low capacitance in the device. It depends on the input supply voltage and the startup current drawn by the motor. If the voltage temporarily drops to low it might cause a reset of the Attiny. As long as the input voltage onto the MCP1792 stays above the minimum 4.5V it most likely won't be a problem.
Another problem can be when the motor starts to run due to the low capacitance in the device. It depends on the input supply voltage and the startup current drawn by the motor. If the voltage temporarily drops to low it might cause a reset of the Attiny. As long as the input voltage onto the MCP1792 stays above the minimum 4.5V it most likely won't be a problem.
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Test Equipment / Re: Magnova oscilloscope
« Last post by Njk on Today at 01:30:23 pm »Rotating the screen would mean removing and reattaching the stand. We don't know if that is supported, and I doubt it. For starters, the handle is integrated in the case and would likely block the procedure. Cooling is passive too, and convection does play a fundamental role, as opposed to forced ventilation. I don't know if putting it upside-down would affect the thermal design, though.So they're experimenting with unusual exterior forms, where the input connectors are located at the side of the instrument. That disposition can be handy in certain use cases. But it will not be unusual for a user to find that the side is wrong and the other side would be better, and the solution is to rotate the scope by 180 degrees. So obvious. Any provision for that?
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Microcontrollers / Re: RIP Z80
« Last post by coppice on Today at 01:29:02 pm »You must have worked on a very narrow range of MCU applications, or perhaps only on small volume products, to have such a view. The vast majority of MCUs produced are quite narrowly tailored to a few applications they suit well. If you don't think the chip is narrowly tailored you probably just don't recognise the applications it was tailored for, You gave no explanation for why an ARM core would be beneficial. Sticking with one maker, and their peripheral set, can be a big speed up in development work. Who cares what the core is, apart from a few special qualities like getting in and out of low power states, where a few designs excel?QuoteIf you try to sell an MCU to many large customers now they show no interest unless it has an ARM core
That however is a reasonable approach.
Nowadays, with a 168MHz core, 99% of applications can be done with 1 or 2 chips e.g. the 32F4xx. These have been around > 10 years, even the chinese do copies, the dev kits are free and well understood by anyone using them, the chips are $5 in quantity, and they are 10x to 100x fast enough for most jobs. I've just done a project with a 32F417 and I am certain I will not need to look at another CPU in the rest of my actuarial life expectancy (20 years). With ETH and USB done and working (not optimally but well enough) and with 21MHz SPI, I can do absolutely anything I have done since 1980 and absolutely anything I can imagine having to do. For highly specialised stuff e.g. a modern DSLR one needs specialised chips, but for nearly all "industrial control" and consumer stuff, more is not needed.
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Test Equipment / Re: Siglent SDL1000X/SDL1000X-E Electronic Load
« Last post by Mortymore on Today at 01:26:56 pm »The batteries I've been testing are those used in small UPS, Pb (AGM) 12v, 6Ah to 18Ah
As usual, the battery datasheet must be observed, but in general for 12V/7Ah, the settings are, I.discharge = 1.2A and V.stop=10.5v (1.75v/cell). Under this circumstances it is expected a 5h test duration and 6000mAh drawn form the battery, if in good condition.
As an example, from the datasheet of the Ultracell UL 7-12 we can extract the test conditions to set (1.2A;10.5v), and what to expect (5h;6Ah)
As another example, according to the datasheet of the Ultracell UL18-12, with the discharged settings as I.discharge=3.06A and V.stop=10.5v (1.75V/cell), the test for a good battery should take 5h and the battery should provide about 15.3Ah
EasySDL has a reported problem of the time axis, with the time stamp being half of the real time.
An example of a test to a Pb battery, 12v/7Ah in end of life
After 10 minutes discharge
After 40 minutes discharge
After 1 hour and 8 minutes discharge
As usual, the battery datasheet must be observed, but in general for 12V/7Ah, the settings are, I.discharge = 1.2A and V.stop=10.5v (1.75v/cell). Under this circumstances it is expected a 5h test duration and 6000mAh drawn form the battery, if in good condition.
As an example, from the datasheet of the Ultracell UL 7-12 we can extract the test conditions to set (1.2A;10.5v), and what to expect (5h;6Ah)
As another example, according to the datasheet of the Ultracell UL18-12, with the discharged settings as I.discharge=3.06A and V.stop=10.5v (1.75V/cell), the test for a good battery should take 5h and the battery should provide about 15.3Ah
EasySDL has a reported problem of the time axis, with the time stamp being half of the real time.
An example of a test to a Pb battery, 12v/7Ah in end of life
After 10 minutes discharge
After 40 minutes discharge
After 1 hour and 8 minutes discharge
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Beginners / Re: Transistor curve tracer recommendations?
« Last post by JohanH on Today at 01:23:44 pm »There is this project, but it seems quite advanced:
https://www.eevblog.com/forum/projects/building-a-diy-curve-tracer/
https://www.eevblog.com/forum/projects/building-a-diy-curve-tracer/
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Beginners / Re: LM317 Based Digitally Controlled Power Supply
« Last post by MrAl on Today at 01:23:38 pm »Hello. I'm looking to construct a digitally controlled power supply. I have a circuit drawn up with a PWM voltage control circuit of my own design, and the current control design that Dave drew on his PSU series hooked up to the input of the second LM317.
After being plugged into a circuit simulator, it seems to have really weird behavior even though both circuits work great on their own. Any help??? Schematic below.
(The +5v inputs are where the PWM will be inputted. An RC filter will be added in the final design. The 1ohm resistor to the far right will also be removed.)
Hello,
A couple points to be made here.
[1]
That 220 Ohm resistor is not considered to be low enough anymore, 120 Ohms is the preferred value now. That's to load the LM317 with at least 10ma.
[2]
When you drive the ADJ terminal directly with a voltage source, you essentially give up the voltage regulation offered from the LM317. The external voltage source appears in series with the 1.25 volt reference source internal to the LM317. That means that your external voltage source is now a large part of the reference source, which means it must be well regulated if the output is to be well regulated. Another side issue is that the LM317 now becomes just a driver, similar to an amplifier with a gain of 1 with an added reference of around 1.25v, and with the external voltage source Vs the reference becomes Vs+1.25v, and that is 'amplified' by the gain of 1 amplifier and then the output of that amplifier drives the output load.
That's probably not a problem, but the external source has to be regulated itself, which for your circuit could be a problem. More about that later.
[3]
The input circuit, ideally, should really be a buck switching regulator that automatically adjusts to the minimum requirements of the input of the LM317. If the so-called drop out voltage was 2.5 volts for example, then the output of the buck should be 2.5 volts plus whatever the output voltage has to be. This isn't too hard to do, but the buck circuit front end is more important because that lowers power dissipation by a very large amount. It means the circuit can go from instead of 30 watts of dissipation for a given load, down to 3 watts of dissipation for that same load. That's a lot and that is why switching regulators make good front ends for linear regulators.
So this means drop the linear front end and go with a buck front end. If you can't do that, then you're going to be stuck with pure linear operation which sometimes will dissipate a large amount of power and require a very large heat sink.
Now a little more about the external voltage source.
Because you will be using PWM, you might have to incorporate some feedback so that you can get the PWM to output the right source voltage so you can get decent accuracy on the output voltage setting. This means sensing the output or the filtered PWM signal and adjusting the pulse width accordingly. This is because the LM317 can no longer regulate the output voltage like it does when only resistors connect to the ADJ terminal. That means you have to do all the regulation with a separate feedback system. This brings in the question of if an LM317 is really needed at all if you have to incorporate your own feedback system anyway and why put up with the unusually large voltage drop of the LM317 that comes with it. With a power transistor and some feedback you can get the voltage drop down to at least 1v or even less.
Presumably, the PWM will come from a micro processor or similar running off a 5V supply. So the stability of the PWM control and the reference voltage to the 317 should be pretty much as stable as whatever supply is feeding the micro.
And you still get the benefit of the line and load regulation of the 317. Not lab quality, but not bad. You will definitely want to calibrate the relationship between PWM and output volts, or like you suggest, measure the output and trim the pwm. That will be slow though, so probably only good for a fine trim.
Hi there,
Actually I was referring to the accuracy of the set point of the voltage that would be controlling the LM317. If the user wanted to output say 5 volts then they would have to apply about 3.75 volts to the ADJ pin. If it was just 3.70 volts then the output would be 4.95 volts. If the design could get that right though (3.75v) I don't think there would be any worry, but that could easily require feedback which brings in the issue of control stability into the picture. If the designer wants to use feedback then it's going to be their responsibility to get it stable. That means the uC will have to sample the output and make adjustments, and that means there will be a delay.
As far as regulating once the right voltage is actually applied, that may be ok but I have not looked into that in detail.
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Microcontrollers / Re: Attiny1606 burning out when connected to a drv8251
« Last post by lavaman on Today at 01:22:16 pm »I feel like i have tried everything. Separately everything seems to work fine, but when connected together it stops working.
I think the only option i havent tryed yet is changing the reference voltage. Not sure if that would make a diffefence.
I think the only option i havent tryed yet is changing the reference voltage. Not sure if that would make a diffefence.
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General Technical Chat / Re: Questions about Adelaide Australia
« Last post by SeoulBigChris on Today at 01:21:45 pm »Thanks! All good information. I’m looking forward to the visit, and if the job pans out, maybe a few more to come.