Recent Posts

Pages: [1] 2 3 4 5 6 ... 10 Next
1
Beginners / Re: Bulk input caps and impedance
« Last post by tooki on Today at 08:15:20 pm »
I'm sure. To give sparks 220uF is not enough (if voltage is moderate). Normal PSU can withtand up to 1000uF. May be not hot plug, those.
The OP’s PSU is running at 36V. That is more than enough to cause visible sparking even at moderate currents. Never mind the quasi-short-circuit current of a ceramic input capacitor, especially if there’s also a ceramic output capacitor.
2
Microcontrollers / Re: CH32V003 using I2C mpu6050
« Last post by SiliconWizard on Today at 08:14:53 pm »
If you've checked everything else, the likely issue is just the slave address. You're using 0x68, which is the 7-bit address. But I2C functions of the SDK (similar to the STM32 HAL, which WCH has gotten its inspiration from) take an 8-bit address IIRC (so the byte that it will send over I2C). In your case, you'd need to shift the address left by 1 bit, like 0x68 << 1. Haven't used the CH32V003, but try this and let me know.
3
Beginners / Re: Bulk input caps and impedance
« Last post by xvr on Today at 08:10:53 pm »
I'm sure. To give sparks 220uF is not enough (if voltage is moderate). Normal PSU can withtand up to 1000uF. May be not hot plug, those.
4
I believe the brother label printers (usually USB, thermal, a wide variety of cheap clone labels available) are supported by drivers within the CUPS printer control system in Linux.
They probably are, but for inventory labels like this, where it’s likely that bar codes are involved, you don’t want to print using regular OS print drivers, you instead want to use the printer’s own command language to ensure that bar codes are printed perfectly sharp.

Well, you *can* do decent barcodes via OS print drivers, but it requires some careful management of the print data to get good results.  Any raster content sent to the printer, especially barcodes, should exactly match the printer's native resolution, and should be uncompressed 1-bit monochrome.  Whether it's worth dealing with that versus dealing with ZPL or whatever will depend on the application. 

Source: I got fed up with Brady's shitty label printing software and stupidly limited printer command languages, so I built my own HTML template -> raster image -> Windows print API pipeline.  I had to jump through a couple hoops to correctly scale the template content to match the print resolution, and manually collapse the color space to 1-bit to eliminate any image compression artifacts, but everything comes out nice and crisp, even with relatively tight linear barcodes.  (Modern camera-based barcode scanners also help, since the image processing has to correct for a lot of other confounding factors anyway.)
Exactly. That effort is precisely why I said you don’t want to use the OS printing (not that it’s categorically impossible to get good results using it*). Using printer commands (ZPL, ESC/POS, etc) ensures you get clean results.

You’re definitely right about camera-based scanning. Even blurry bar codes seem to scan well. Heck, I find it almost annoying (on principle alone, as a perfectionist) that my bank’s 2D bar code scanning (for 2-factor authentication, and for scanning bills) recognizes codes before the camera has even finished focusing on it! I’ve also had no trouble scanning bar codes in PDFs where the bar code is stupidly saved as a bitmap image, which a lot of software will then apply an interpolation filter to when scaling for printing, resulting in blur. (It’s definitely better to have it as a vector “font” or vector graphics, so that it always prints sharp.)

*I worked at the Apple Store many years ago, and their receipt printers use OS printing so that it can print in the corporate font instead of the printer’s ROM fonts. They had clearly worked out how to get clean bar codes, of course. But the text is actually not great, you can tell the font is not optimized for low resolution. As far as I can tell, their POS system still works that way to this day.
5
Repair / Re: Rigol DP712 Output Shorted; Fuse? / I Screwed Up
« Last post by zanfar on Today at 08:09:30 pm »
One last question: is there anything special about the compound between the TO-220 package and the heatsink, or is it normal thermal paste? I have verified that the heatsink and package case are electrically connected in the factory state, so I shouldn't need anything insulating.
6
General Technical Chat / Re: Is LinkedIn worth keeping?
« Last post by SiliconWizard on Today at 08:06:59 pm »
I initially thought of it as a Facebook for work related stuff. So you could make use of the contacts you have at work and not have them see the crazy stuff you get up to at the weekend.

I avoid it mostly as it wants to be a job advertising website and is infested with agencies trying to sell me a job that I left years ago.
Some of the headhunters are completely useless. I had one that cold called me on my work phone to try to poach me. I was sitting 1.5m from my boss.

I've had a headhunter call me at my workplace too, company phone! - which I thought was pretty dumb.
7
Microcontrollers / Re: CH32V003 using I2C mpu6050
« Last post by jlsilicon on Today at 08:06:02 pm »
MPU6050 board HW-123 has built in Pullup resistors.
Yeah thanks, I did check that.

https://europe1.discourse-cdn.com/arduino/optimized/4X/7/4/6/74631f82563988409a5cddf32fdacbfee3e4707f_2_690x403.jpeg

8
With many individual resistors the change in the resistors is a lot of work. An alternative could be dropping the supply voltage with a few diodes in the supply or a change in the 5 V regulator (e.g. to 3.3 or 3.6 V).

For a little more powerfull version, there may be 74AC595, though the higher speed also make the signal integrety a possible issue.

PWM typ dimming could be used for a intensity reduction but is not reducing the peak current. So it hardly solves the drive limitations or the 595.
9
Beginners / Re: Bulk input caps and impedance
« Last post by T3sl4co1l on Today at 08:00:42 pm »
Quote
If I put a cap directly across a DC barrel jack input, then when I connect the power to it, I will get a spark
There is should not be with simple capacitor. Especially with 220uF. Something definitely wrong. May be capacitor was plugged in reverse, may be rated voltage of capacitor is much less that PSU output.

Normal PSU should not even notice capacitor of such value.

Are you sure?

What are typical values for output capacitors on a PSU?

What happens in the instant such a supply is hot-plugged to a discharged capacitor?

What happens to a mechanical contact (such as a hot-plugged connector) in the instant it becomes conductive?  Could sparking occur?

Tim
10
Security / Re: Microsoft repackages apps with a telemetry .NET wrapper
« Last post by tooki on Today at 07:58:59 pm »
Telemetry is fine but Microsoft's approach to telemetry is akin to punching someone in the face and saying afterwards that there's instructions on how to say no in a filing cabinet in the basement of the local library while telling you to accept your face punching, shut up and calling you a peon.
From skimming the Twitter thread, nothing was hidden, the developer just wasn’t paying attention to things when packaging their app for the MS Store.
Pages: [1] 2 3 4 5 6 ... 10 Next