Recent Posts

1

Manufacturing & Assembly / Re: Brief review of the Zhengbang ZB2520HL reflow oven (T-962A alternative)

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

Hi.
I just collect my RF-A350 oven, I did not try any PCBs yet but when I checked build in reflow profile without any modifications and with thermocouples stick to bottom plate it doesn't look good.
Temperature in the middle is follow the profile but overshoot 5-6 deg. Temperatures 10 cm from middle, each side, seems to also follow profile but are under the line sometimes 10-15 deg, but within few extra seconds they starts following middle temperature.
Can someone share settings or other tweaks for this oven as factory one seems to be not perfect.

Attached factory profile 4 with empty tray.
Regards

I've not done any tweaks, just been using curve 4 and getting good results.  It works so much better than my 6 year old T-962A which would either burn connectors or not fully melt the solder, both happening on the same PCB unless is was really small and placed close to the center of the tray.  I've not run any large inductors, but I've had some batches with various SMT inductors, relays, electrolytic caps, and connectors go through it fine.

You really need some thermal mass and the thermocouples attached to that to get any real sense of how well it follows the profile.  I did a trial run some time ago with a temperature logger, but I don't seem to have saved the data.  I'll have to do that again when I get a chance.

The curve I posted above as measured by the ovens own thermocouple was pretty accurate to the settings - it will never be perfectly even in every part of the oven.

I sit my pcbs on small metal standoffs under the corners or edge rails to keep the PCB slightly above the tray.  Possibly not as critical as on the T-962A which just had bare metal.

2

Test Equipment / Help me chose my pogo pin for THM Test Points on my PCB plz

« Last post by fishywisky on Today at 08:10:39 am »

Hello everyone,

I have a slight problem. I'm in an internship and don't know much about Pogo pins. I wish to select a type to come and touch the THM test point on the board that is given to me. The test points look like the ones in the linked picture. If anyone could help me, it would be really nice.

Have a nice day!
(Sorry for my poor English)

3

RF, Microwave, Ham Radio / Re: Cascade RF Frontend 2.4GHz possible?

« Last post by vk4ffab on Today at 07:59:48 am »

Please see attachments for Front, back side and the circuit I want to use.

My gut says, nope, bad idea. The RF in and Antenna ports have maximum ratings of 5dbm into them and you want to blast almost 1/2 a watt into it. The output power from one of those chips should be 22dbm. BOOM dead chip. Just buy a new router.

4

Manufacturing & Assembly / Re: Brief review of the Zhengbang ZB2520HL reflow oven (T-962A alternative)

« Last post by Kean on Today at 07:59:25 am »

I have the ZB3530HL & have attempted to use the software provided for the ITECH RF-A350. The software connects ok (the ZB3530HL displays "PC Link" on the LCD). I'm using a USB-Serial lead on Windows 11. When I press "Run" with a suitable configuration, the machine does nothing & the "Now" section at the top shows nothing in the Temperature field. I've tried with flow control & as admin.

I've tried searching for an answer online to no avail. Has anyone been able to get this working successfully & what's the trick?

Pete

I've been meaning to try the PC software myself, so last night I asked ITECH for the RAR file password and today I hooked up a laptop with a USB to RS232 cable and the cable provided with the oven.

I started the software, selected COM4, and clicked Open to open the port, then click Link and I for the same "PC Link" message on the oven LCD.  That is a good sign it is communicating.

I entered some reflow parameters (similar to the built-in Curve 4 that I've been using) and hit Run.  Everything worked as expected, with the set points and hold times as specified.

Screenshots attached.  The Y axis of the graph is 25C per div, and X axis is 45 seconds per div.

My main complaints are:
- You can only specify set point and hold times, but I guess that makes sense as it can only ramp up or down so fast.
- It is quite slow in the cooling phase, taking 9 or 10 minutes to cool to 100C in my case unless I open the door.  Would be nice if it ran the fan faster.
- The PC software is really basic.
- The graphed temperature curve is restarted if the time exceeds the full width (900 sec/15 mins) which my settings do (only just).
- The graph also blanks after the run is complete.

5

Test Equipment / Re: JunTek PSG9080 Programmable Signal Generator (80 MHz - 300 MSa/s - 14-bit)

« Last post by eTobey on Today at 07:57:58 am »

How does this look to you?

I added a plastic washer under that screw on mine.

Allthough it does not answer my question, it is still a good suggestion. 

To me it looks like "Guys... we fucked up. How can we fix it? ... we are lucky, there are no traces, and we can just drill a hole."

How are these BNC sockets held in place? Just by those connections?

I was just about to order this product, when i saw this. Now i ordered a Rigol for the same price.

6

Test Equipment / Re: Standardised Way To Test Oscilloscope Screen Update Rate

« Last post by EEVblog on Today at 07:57:55 am »

With mouse plugged into the scrope the scroll wheel is available for making numeric field adjustments.

That's interesting, must not have implemented that in the web interface

7

Test Equipment / Re: Standardised Way To Test Oscilloscope Screen Update Rate

« Last post by EEVblog on Today at 07:56:08 am »

This really is a non-issue which has been discussed before. Any form of high-waveform update rate will have a certain amount of persistence time to make sure the signal stays on the screen long enough to be noticed. Think in order of magnitude of 200ms. Anything below is likely to be missed. If you think about it and think back about the relative long fade times of phosphorus used in CROs, you'll come to the conclusion that the display update period can't be a parameter in the process which shows the signal.

Sure, but why does any scope update the display faster than 200ms then?
I for one prefer the apparent faster updating of the 2000 vs the 1000

8

Microcontrollers / Re: SD Card reliability in SPI mode

« Last post by TizianoHV on Today at 07:54:59 am »

I've used a 2GB Kentron and a 8GB Kingston micro SD card + SdFat for my datalogger (Arduino nano every).
I wrote into the same cards for weeks, 50 times per second (2kBytes/s), multiple times without any issue.
Maybe smaller cards are better for such applications?

Code: [Select]

...
dataFile = SD.open(filename, O_CREAT | O_APPEND | O_WRITE); //Open file only once
...

while...{
  ...
  dataFile.println(dataString);
  SDbuffCount++;
  if(SDbuffCount > SDbuffDim){
      dataFile.flush();        //Flush, up to 5 times per seconds
      SDbuffCount = 0;
  }
}
dataFile.close();


9

Test Equipment / Re: Choosing between entry-level 12-bit DSOs

« Last post by Fungus on Today at 07:53:03 am »

Can the TSA do amplitude modulation?
Put in some AM at about 10% of the frequency.

It only supports a limited number of amplitude levels (I think 8 or so) for the the modulating signal, so it's a "stair step sine wave".
And the modulating signal is limited to 10 kHz.

EDIT: See also Erik's video: https://youtu.be/U2cw0bmuSLM?t=239

The TinySA supports 8-point interpolation, while the Ultra can muster up to around 128 points depending on modulaton frequency.

Ok, no problem.

I'm just wondering how the Siglent is cheating to get that display. The Rigol isn't doing anything wrong, it's doing the correct math for the limited information it has.

The original Signal can be reconstructed with much wider filters but they'll only work if the signal is perfectly periodic.

I was wondering what happens if the signal isn't periodic. It could go very wrong.

10

Power/Renewable Energy/EV's / Re: 5 out of 6 vendors are scamming people with wrong crosssection of cables

« Last post by eTobey on Today at 07:50:45 am »

... I ask because measuring cross section of a multi-stranded wire is not trivial at all. Which is also why, to answer your question: I have never checked. I think the risk of me measuring incorrectly would be larger than the manufacturer lying.

Current, voltage drop and ust a few calculations, and then you have the cross section. Nowadays with internet i would call this trivial.

I could not find the very same measurments, but i can give you an example, that is as good. (Scamed by the PCB manufacturer, as he did not mention a tolerance of 20%. Seems to be a chinese thing, yes).