Recent Posts

1

Projects, Designs, and Technical Stuff / Re: Vacuum Fluorescent Display Driver

« Last post by bostonman on Today at 02:15:37 am »

I saw that note about protecting the outputs and considered a buffer (I thought more of an unity gain op-amp).

I wasn't sure if a buffer or op-amp would affect rise/fall times causing errors.

As for connectors, I'm using: 7282-6SG-300 and 6282-6PG-3DC

The connector was slightly larger than the available BNC hole(s) on the rear, so I ground the hole larger. My plan is to tap off the main PCB to shorten the distance and then make a cable that is long enough to have the display mounted on the front. If I'm going with buffers, then maybe I can just tap off the daughter board I made.

Just wish I had thought of this when I made the daughter board, now I need to tap off the taped off board.

2

Repair / Re: Yet another Fluke 8050A LED display conversion

« Last post by gcwills on Today at 02:07:45 am »

Thanks low impedance for your post. As I'm using common cathode displays I attempted  Rich's PNP with no success and also the 2n7000 arrangement with no results.
As the link that you refer to indicates, the methodology Fluke used to drive the + and - LCD display is unusual,,,,,

3

Projects, Designs, and Technical Stuff / Re: On using a single Ethernet cable for communication and two activity LEDs

« Last post by NiHaoMike on Today at 02:07:37 am »

Add 100nF capacitors on the source end, after the current limiting resistors. It would slow down the edges a lot but would still appear instant visually.

4

Power/Renewable Energy/EV's / High voltage banana plugs ?!

« Last post by JeLo on Today at 02:04:28 am »

For some odd reason I need to connect a banana plug to a EHV cable. It's low current and I got no other option available. Basically it's to replace a cable from a CRT rejuvenator that is kind of different from most and also uses the anode connection. The part that connects to the CRT is practically 30Kv, as is normally the case for most bigger tubes, but the part that connects to the tester / rejuvenator is actually a freaking banana plug! And yes, it's it was like that originally. It's from a reputable brand in Germany that has since closed doors.... Doesn't matter, the thing here is I couldn't find any banana plugs speced to 30kv, so probabably the device didn't work at that voltage either... But I wanted to use a secure connection without much hassle at the same time.
Anyone knows a source ? I'm tempted to try a simple audio plug at this point, but so far have resisted it ...

5

Projects, Designs, and Technical Stuff / Re: Highside MilliCurrent

« Last post by sourcecharge on Today at 01:53:12 am »

So why not just use TI's INA290? Its a couple of bucks, handles up to 120V common mode, has 1MHz BW for the lower gain version, and CMRR of 140dB.  You are really going to struggle to match that using opamps and discrete resistors.
While I applaud the OP's efforts to 'roll-your-own' (not enough ppl try to do this) some things are much better done on a single chip.

The price is nice, but its a sot-23-5 and I've sworn off using those along with the tsops.

Too small for me, I only like using soic packages as I hand solder them on.

I don't need 120V but it does seem like this would be better input range for a universal highside current meter. 

I think there are current sencing amplifiers that have high common mode voltages too but they use the input voltage to offset and power the chip.

The 168db of CMRR on the opa189 or opa2189 and the low offset is worth it though and I'm happy with what I made.

6

Projects, Designs, and Technical Stuff / Re: Different die pictures

« Last post by D Straney on Today at 01:50:55 am »

Huh interesting, good to know - I obviously haven't worked out the macro-scale resonant parameters based on typical quartz Young's modulus & dimensions (would probably be orders of magnitude off, then), but given the frequency I guess it shouldn't be surprising it's much smaller-scale propagation, and not damped by air resistance etc. the way it would be if it was actually bending the crystal lengthwise.  Sounds like it's the thickness that's really the key parameter then.

In that case, wonder why it's arranged as a cantilever in the Noopy's small crystal: only reason I can think of as a non-expert here is that it's about giving it a non-rigid mounting for some level of vibration isolation (and/or CTE mismatch between it and the package, over the longest dimension?) - the discs are mounted on flexible bent pins, and some even sit on wound springs (see the top-right one in my photos above).  Can imagine it was harder to isolate the smaller crystal that way within the form-fitting package and low height - maybe the manufacturing process wouldn't have worked with some flexible crystal posts bonded on the inside, and it was easier to just mount it rigidly at one end, and use the bulk material properties of the quartz to give it flexibility.

7

Projects, Designs, and Technical Stuff / Re: Bluetooth rotary phone from PTT T65

« Last post by Zipdox on Today at 01:41:31 am »

Seriously? Your EasyEDA thing doesn't have a lot of symbols not available in KiCAD (I didn't find any except for the screw terminals). And making a new symbol takes at most 5 minutes (if it's really complex).

There's probably a way to do it but I'm lazy. This is more of a gimmick project.

8

Repair / Re: For those with experience in AC motors, what is the reason of this noise

« Last post by Kjelt on Today at 01:34:29 am »

The plate on the motor states 220V 50Hz delta connection so single phase which normally needs a starter capacitor for the phase shift to the third connection.
But do verify that the motor is still in delta configuration.

9

Microcontrollers / Re: Can your program, ever damage an MCU ??

« Last post by MLXXXp on Today at 01:32:24 am »

Or have code that writes excessively to flash or eeprom and wears it out.

I think this would be one of the easiest ways to damage an MCU under the stipulated guidelines.

10

Programming / Re: My code is ugly

« Last post by pqass on Today at 01:31:47 am »

My solution involves two floating-point ops per digit read which may be time-costly on a 8-bit MCU.  But at least there are fewer iteration, index, and temp vars to manage (and debug).

sizeof returns bytes allocated to the whole type/var x so dividing by the bytes used by the first element, x[0], returns number of elements.  No need to create a #define for every array; can just drop in a one-time number at the array definition.  It's portable, type independent, and no overhead as the value gets resolved at compile-time.