Recent Posts

41

Power/Renewable Energy/EV's / Re: SMPS input filter cut off frequency

« Last post by jpanhalt on Today at 08:26:52 am »

Neither Basso, nor ti.com, nor any other reference that i can find make this stipulation. Why do
VicorPower stipulate it?

Capt. Obvious: Have you tried asking here: https://www.vicorpower.com/technical-support

42

Other Equipment & Products / New Aixun T380

« Last post by SteveyG on Today at 08:26:24 am »

Aixun recently released a new portable station, the T380
https://www.aixuntech.com/product/t380-portable-smart-soldering-station-with-t210-t115-handle-welding-tools/
https://s.click.aliexpress.com/e/_DFbqYEb



It looks like you can power the station from the included USB-C power supply, or run it from the replaceable lithium-ion battery if you need to work away from your work bench.
It's surprisingly heavy, but appears to be fairly thick completely metal construction.
I should have a video on Monday

43

Test Equipment / Re: SDS800X HD - Issue disscusions - is it me, or the scope?

« Last post by electronics hobbyist on Today at 08:25:47 am »

Yes, we only discuss technical issues. If the problem is easy to reproduce, the manufacturer can solve the problem quickly. @eTobey You can attach two pictures, one picture where we can see the complete signal, and the other picture when there is a problem.  And explain the configuration of qualified, can also use pictures.

44

RF, Microwave, Ham Radio / Re: RF 2.4GHZ through Via

« Last post by tszaboo on Today at 08:21:11 am »

I don't think the via is the issue.

I see two immediately obvious issues on the layout, that should be addressed first:
1) Your antenna has no matching network. Place at least a PI in between the antenna and the switch. Someone also need to connect the antenna (and the added pi network) to a VNA, and measure it, and select the right value components. This needs to happen 100% on every PCB antenna designs, and it's not something that you can just simulate or copy.
2) I don't think the antenna layout is OK. You copied the ground plane clearances, but you didn't place the antenna in an optimal orientation.
3) Your SMA might not be 50ohm with this layout.

But even without both of these fixed, you should have some reception, which makes me think there is another, more fundamental issue with your system. Meaning that having both these fixed will improve your signal maybe 20-30dB, but two boards next to each other should 100% be able to communicate with each other, since they have something like -90dB link budget. Something else is blocking the RF completely, like timing, channel selection, software...

45

Beginners / Re: 555 driver and Transformer questions

« Last post by Zero999 on Today at 08:20:47 am »

It's the V*I*t which is important, not just the voltage and frequency.

A 120VAC 60Hz transformer will be fine if the voltage is also reduced, as well as the frequency. It'll be able to work at 12VAC 6Hz with no problem. If the insulation can handle the extra voltage it'll also be fine with 240VAC at 120Hz, although there will be additional losses due to eddy and hysteresis, which will increase the off-load power consumption and heating.

Presumably you're using the transformer in fly-back mode, which is different to how it was designed to be used.

Which winding is connected to the 555 circuit?

Is it just single ended or push-pull?

Post a schematic.

46

Beginners / Re: 72C5 - What Is This?

« Last post by Trurl on Today at 08:19:43 am »

The photo above shows the side(auxiliary) board of the PSU with one of the "72C5" parts towards the center(use slider at bottom of this post to move to the center of the photo). I've marked the connections as follows;

Pin 1 (Blue) :    Adjacent via connects to Microchip dsPIC33FJ64GS606 pin 26 (VDD) (towards the right side of the photo)
Pin 2 (Yellow) : Connects via resistor "91B" to the LM393 opamp's pin 5("+" non-inverting input)
Pin 3 (Red) :     Via connects to the +12VDC main output of the PSU

Thanks in advance... Cheers...

47

Beginners / The old "Replace blue LEDs with red LEDs" 7 segment question (74HC595)

« Last post by trondl on Today at 08:18:51 am »

Hei from Norway!
I'm posting it here in this section as I'm a n00b in the technical sense when it comes to LEDs and current limiting.

I have an older (2011?) Mytek USB-DAC with seven blue 7 segment displays that after the years have gotten dimmer on the most used segments (48 kHz...), making it look like "burn in".
Is this evidence of early blue LEDs wearing out faster?
The unit has seen 24/7 on highest brightness.
It is dimmable, and on the lowest setting, the LEDs are somewhat similar.

I have gotten access to the front panel parts and layout document from the company, but not the schematics.
The unit is seeing too much usage to give it downtime for poking around yet.

What I can see is that the thru-hole 7 segment LEDs are Lite-On LTS-2801AB (3.8Vf @ 20mA If, common anode).
They seem to be controlled by a 74HC595A per segment and have a 220ohm current limiter per line.
Since the Vf is 3.8, I believe the 595 is running at 5Vcc.
Could this also be a symptom of failing Shift Registers? Doesn't quite seem logic to me (pun?).
I've heard rumours that a 74HC595 isn't ideal for driving LEDs, and can wear/burn out.
Also, how does dimming work on a 595?
PWM?

LTS-2801AB is obsolete, and I'd wish to replace them with the red LTS-2801AP (2.1Vf @ 20mA If) which is still somewhat available, or an equivalent.
I have a hunch that red LEDs last longer, and I prefer them for not being so intruding on the eyes (who doesn't?)

I've tried to find other alternatives, but the physical size seems to be a limiting factor: (h)10mm x (w)7.4mm x (d)6.1mm.
Is there a "standard" size for 7 segment displays?

Now, the main question of course, can red LEDs with ~2Vf last longer than 2 seconds in this circuit?
3.3V seems to be available on the PCB for driving an IR receiver.
Run the 595 on 3.3Vcc instead?

Thanks in advance for your time and input!

Mvh
Trond

48

Other Equipment & Products / Re: Miniware MHP50

« Last post by SteveyG on Today at 08:17:39 am »

Apologies for the long delay, I've release the video on this finally.
It took a while for my PD3.1 power supply to arrive, but it works well at 28V

49

Test Equipment / Re: SDS800X HD - Issue disscusions - is it me, or the scope?

« Last post by ebastler on Today at 08:09:15 am »

We are blue in the face from telling such, so much so I think ears must be just painted on.

How is this type of comment supposed to be helpful? It's only stoking up controversy. Please bite your tongue and refrain from posting such insults.

50

Metrology / Re: ADR1001 - Ovenized Voltage Reference System

« Last post by iMo on Today at 08:08:51 am »

Milpitas list..
I see there only two parts usually discussed here - LTC2057 and LTC665x..