Recent Posts

1

Projects, Designs, and Technical Stuff / Re: role of optocoupler for biasing drain of amplifiers

« Last post by xvr on Today at 05:02:44 pm »

> For that i need to tune the bias for my single amplifier and to tune sepratly for the pair.

Nothing. Your schematic do not depends of amplifier current (6A for single, 12A for pair), only for amplifier voltage. Voltage the same for both single and pair.
But you need 3 identical channel (including DC/DC and UCC) for control 3 independent subcircuit (1 single + 2 pair)

PS. Consider P channel MOSFETS from my previous post - your current schematic became monstrous 
PPS. Your currently selected MOSFET do not fit to your requirement: only 4A of Id and large Rdsonn - 0.1Ohm. Consider something more powerfull

2

Test Equipment / Re: new killer scope in town - a true game changer from R&S - RTB2002 & RTB2004

« Last post by electronix27 on Today at 05:00:48 pm »

This last thing may be of use to someone.  Decided to purchase four new probes.  According to the Rhode and Schwarz website, I could purchase new probes directly from the company.  Support told me as an individual, not a company or part of a company, they could not help me.  Something about being in the process of changing the way they deal with non company purchasers.  Maybe US market only.

Considered some other options, but decided on OEM probes.  The only place to purchase these in the US currently is TEquipment.  So I ordered four RT-ZP03S probes.  The image, description and specs listed were exactly the same as RT-ZP03 probes, 1X/10X switchable attenuation.  Upon arrival I found the RT-ZP03S are actually 10X only, and all three waveform adjustments are now inside the small enclosure at the BNC connector.  They work, but I really do prefer the switchable attenuation.  Possibly the original RT-ZP03 are no longer made.

Part of the reason I purchased this scope for the higher cost was the claimed superior support.  Other companies may have the same protocol.  Nonetheless my last Rhode and Schwarz purchase.

Russell

3

Beginners / Re: Is it safe to store CMOS devices in the AideTek ESD Boxes

« Last post by shabaz on Today at 04:59:27 pm »

It may get unscalable when everything is stored in individual small compartments. Personally, I leave ICs in their original packaging, and just write with a permanent marker in case the labels fade, and place them all into a box (over time, you could have a separate box per project or separate boxes for (say) analog ICs, discrete semi, digital. Some boxes are long and about the right size to keep all the packets tidy-ish if you prefer that. For anything in tubes, personally, I use a small waste bin (well, slightly nicer than a typical waste bin! It is woven to look not so ugly) and place them all in there (in their original packaging again).

For general practicality while experimenting (i.e., not production), I do have little conductive plastic pots with lids in a couple of small shallow tray-like boxes with lids. These are useful for your most popular devices, e.g. low-power (SOT-23 or similar) BJTs, MOSFETs, diodes, jellybean stuff etc, so you don't need to keep trawling through large boxes for those. But possibly it's still a bit excessive, a simpler option would be to keep a small box of popular parts in their original packaging. Whatever you feel is more practical for you. You can also place conductive foam in ESD-safe tray-like boxes if you have popular through-hole parts.
 
In your case, since it is a specific lab kit, you may wish to do something different for even more practicality perhaps, but I'm not sure there's any single optimal way. One reasonably practical way that I saw was the Digilent component kits. They use a cheap (non-ESD-safe) clear transparent plastic box with dividers, and for the ICs, they shoved them in foam and inserted them into compartments (also, in the photo, notice the chamfered corner on the foam; that's for lifting out because there are more ICs in another layer of foam below). Obviously, this is not good for production use, as there is still a risk of damage, but for learning/experimentation, I think it's a fairly reasonable solution to obtain a large box with many compartments and a large sheet of conductive foam and cut it up. If your lab kit is really massive, perhaps it could be split up into two or three categories, each in its own large box.

4

Test Equipment / Re: Troubles with HP-8903B

« Last post by Tony_G on Today at 04:52:03 pm »

My 8903B sits pretty nicely around 999Hz (value will change while the unit warms up) when set for 1000Hz and 1V with a distortion reading of 0.0021. No filters, power-on defaults apart from amplitude.

I think your unit is fairly sick - Grab the manuals from ArtekManuals.com to help you track down the issue.

TonyG

5

Metrology / Re: ADR1399 reference

« Last post by EC8010 on Today at 04:51:37 pm »

My ADR1399 (TO46 variant) evaluation board arrived a few days ago. I replaced the 1k33 resistor with a temperature compensated LM334 set to 3mA. The periodicity is due to the central heating coming on in the (cold) lab, probably a change of 5C or so. Deviations are smoother and smaller than with resistor. Negative polarity is because I inexplicably plugged to the board the wrong way round and didn't notice. 

Power was 12V 7Ah lead-acid battery, meter was HPAK34470A.

Next step will use op-amp bootstrapped Zener circuit instead.

6

Beginners / Re: Dimming signal 0-12V from microcontroller (logic level to 12V PWM)

« Last post by Damon on Today at 04:49:57 pm »

I've ordered several OpAmps (TLV272ID, MCP6H81-E/SN, TS912D, LMC6482IM, basically every Rail-to-Rail output capable 12V tolerant OpAmp below €2 that Reichelt had in stock).
After completely wasting my time yesterday because I didn't realize my breadboard has separate power rails left/right along the long side... 
I managed to get a smooth voltage controlled via PWM using this circuit:



I've tested it with +5V supply on the MCP6H81 and it works as expected.
Good thing I bought some trimmers, since the fancy metal layer resistor kit have flimsy leads that barely make a connection with the breadboard...

Next I'll test it with the 12V aux supply from the lamp and then I'll connect it to the dimming input,
if that works well I'll try to design a proper PCB with some off-the-shelf 12V to 3V3 DC/DC converter module as a supply for the ESP32 devkit.

Maybe there will be a rev.2, I just found an old LDR and I have some spare OpAmps (2-channel ones too),
but currently I have no idea where I could mount that thing to expose it to ambient light.

Now my last concern is protecting the dimming port. The highest voltage I've measured was 11.2V with the stock pot.
I can't imagine an additional .8V would hurt, but just to be on the safe side, I'd like to add a zener diode for protection across the V_DIM output to ground.
That won't interfere (below 11V) with the OpAmp output, does ist?

Edit: BTW I don't know why I constantly mix those up, my Oscilloscope is an Hameg HM203-4, not a 205. Crusty but trusty.

7

Repair / Laser Level Charger PCB ID

« Last post by Shaky on Today at 04:47:07 pm »

Hi all. I have had a look at a battery pack out of a Datum NE-1L Laser Level for a mate that isn't powering the device. The cells are 2 x 26650 Li-ion in parallel and test fine. However, they don't output any power and also won't charge. The LED is a 2-colour unit, the green is OK (charging complete presumably) but the red (charging in process presumably) tests short circuit. When the wall-wart is turned on, it is outputting the correct voltage but the LED's on the battery pack don't illuminate. It's pointing to the charger/bms unit being faulty I'm guessing.

Trying to get hold of a replacement pack is proving fruitless (and expensive if they were available) so I decided to see if I could source a replacement/compatible charger PCB. However, there doesn't appear to be many markings on the board that result in any suitable results from Google etc so I was wondering if any of you guys here could point me in the right direction, or am I fighting a losing battle ?

Pics uploaded of course 

TIA.

8

Beginners / Re: What function generator, that does a bit more than just a simple signal

« Last post by shapirus on Today at 04:45:42 pm »

Can you please check if my tool to read/write arb waveform for PSG9080 works with JDS2800?

just connect it to PC and try to execute:

Code: [Select]

PSG9080_ARB.exe COM3 -read 1 wave01.txt

where COM3 is a port which appears when you connect signal generator to PC.

hmm... COM3, sounds like something from the ancient past. I think I had my 2400 baud modem on COM2 and mouse on COM1 in mid-90's.

Jokes aside, I'll try some time later. Of course I'm using Linux. Will see if it works with mono.

9

Projects, Designs, and Technical Stuff / Re: role of optocoupler for biasing drain of amplifiers

« Last post by john23 on Today at 04:44:56 pm »

Hello XVR, I have 5 amplifier i need to power.Single and two pairs.
 I want both to be able to power a single amplifier and a pair from a single Vds and Vgs.
For that i need to tune the bias for my single amplifier and to tune sepratly for the pair.
Is there a clever way to tune to Vgs and Vds .
Its basicly a thing of a load.

10

Projects, Designs, and Technical Stuff / Re: (Yet Another) DIY Multislope ADC

« Last post by Kleinstein on Today at 04:42:52 pm »

The faster locic chip usually add less jitter, though it is not a direct link. I had a hard time finding some jitter specs for the logic chips. An an analog devices application note (AN 501) there are a few numbers:
74HCT... ~ 2.2 ps
74ACT... ~ 1 ps
74LS...      5 ps
The 74LVTH and similar modern CMOS series are likely more like the ACT.

Depending on the code to run, one may not need that much clock. After all the RP2040 has 2 cores. So not need to get close to the 50 MHz max for an external clock.
In my ADC version I use only 8 MHz, though I see it getting tight in some places to do the math. The same clock for the sync and RP2040 is definitely a good idea. If the PIO runs slower one would still want a phase adjust step and than could still use the PLL for the µC clock.
A direct USB link and thus need for the 48 MHz is not really there, as one usually wants an isolation layer to USB.