Recent Posts

1

Projects, Designs, and Technical Stuff / Re: MCP3008 and MCP23017 experiments - first project verification

« Last post by moffy on Today at 12:49:01 am »

Additionally, I've added resistors to drop the supplied voltage to the chips to 3.3V, even though they can function at 5V, which might be unnecessary.
I have included ZIP file containing KiCad project

Just an FYI, not everyone uses or has Kicad, if you want a broader input, if you post your schematics etc as JPEG or PDF no one will need specialist software to view what you post. Secondly resistors make poor voltage drops because their voltage linearly depends on current which can vary. If you want to drop from 5V to near 3.3V, use a couple of series diodes, they'll drop between 1.2V to 1.5V in normal operation, this is not a comment on whether it is desirable or not.

2

Repair / Re: Rivets/eyelets for PCB repair

« Last post by mightyohm on Today at 12:33:27 am »

Rembrandt electronics in the Netherlands is selling copper eyelets on Ebay.  You can get a nice assortment of various sizes for around $22 USD.  They also sell small lots of one size.  Just search for TH eyelets

It looks like the Rembrandt store is down due to family health issues - that doesn't sound good. Does anyone have a good source for inexpensive rivet assortments, or knows where Rembrandt was sourcing their rivets? I could use a handful in the smaller diameters and it looks like the Aliexpress rivets are larger.

3

Test Equipment / Re: Siglent SDS3000X HD and upgraded SDS1000X HD

« Last post by gburdzin on Today at 12:32:44 am »

Hello,

the SP3050A probes are also included in the SDS2104X HD.

Best regards
egonotto

My SDS2104X HD (received just after Easter) also came with the SP5050A probes.

4

Manufacturing & Assembly / tough sheet dielectric material?

« Last post by coppercone2 on Today at 12:30:54 am »

What is a good brand of tough dielectric material to cover a chassis segment?

I use double sided sticky high temp silicone glue kapton sheet. but its still kinda thin, also expensive

Is kapton the best material for this? I mean something that can armor it a bit from getting banged by a loose transformer or something like that. like in the inside of a welding machine

Kapton thick is only 10 thousanths or so usually. I mean something thick like 30 thousanths and pre adhesive lined (sheet adhesion always comes out like shit), and durable for high temps. Maybe kapton can go on top of this material that acts more like armor then insulation..

5

Repair / Re: FUG HCN 14-12500, High Voltage Power Supply repair

« Last post by MathWizard on Today at 12:28:35 am »

So what would happen if you put your finger across 12kV ? What about each hand across it ?? Play it safe.

I have a couple of old CRT scopes, IDK how their HV is doing, but I'm not in a rush to find out.

6

RF, Microwave, Ham Radio / Re: 120 or 125 ohm coax

« Last post by LaserSteve on Today at 12:26:19 am »

Use the HP Appcad freeware  and design your own with standard size tubing and some oddball dielectrics or spacers ?

Steve

7

Test Equipment / Re: Siglent SDS800X HD 12 bit DSO's

« Last post by KungFuJosh on Today at 12:22:48 am »

You may want to step it up, and get a better one. You cant expect everything from a 4000€ scope.

100%. He should send me the SDS3000XHD and get himself the SDS7000A. 🤔

8

Test Equipment / Re: DMM Input Capacitance

« Last post by KungFuJosh on Today at 12:21:11 am »

Interesting. I tried that on my SDM3055X-E, and the DCV ranges did have a small impact. 20V to 1000V was 10pF higher than 200mV to 2V.

No effect at all for ACV.

What do you see when switching from DCV to ACV wrt the capacitance between terminals and + or - terminal to ground?

All previous tests were terminal to ground.

SDM3055X-E between terminals:
Auto (200mV):
DCV: 66.27pF
ACV: 58.54pF


SDM3055X-E Positive Terminal to Ground:
Auto (200mV):
DCV: 62.61pF
ACV: 54.18pF

Interesting that there's 4pF less ref to ground vs. terminal to terminal.


SDM3055X-E Negative Terminal to Ground:
DCV: 559.2pF
ACV: 559.3pF

9

RF, Microwave, Ham Radio / Re: Detecting very low power motion sensors

« Last post by LaserSteve on Today at 12:17:15 am »

At point blank ranges you would use broadband horn antenna sets or for hobby use, a set of Log Periodic antennas  by a fellow named  WA5VJB :

https://www.wa5vjb.com/products1.html

Waveguide beyond cutoff issues and Horn  bandwidths  are outside the scope of my post. 

This can be a very tricky problem, especially if FMCW or other modulations are used.

You may need to search up to the millimeter wave bands, and that gets tricky.

Steve

10

Projects, Designs, and Technical Stuff / Re: custom LCD design

« Last post by PCB.Wiz on Today at 12:13:45 am »

@Kim Christensen yes that would definitely make sense for the first couple to just take a off the shelf parts.  I was hoping to skip a step but I should probably do a 6 digit seven segment for the top and put a separate 16 or 20 x1 character display on the bottom.

I did find a nice, large 7 segment display (but no modules ?).  This has 131 x 30.5 image area.
https://www.aliexpress.com/item/1005003087294038.html

An alternative would be 3.12" etc OLED displays 256x64 - this has a slightly smaller 79 x 21 active area, but is far more flexible in what can be displayed.
https://www.aliexpress.com/item/1005004150204885.html

or 5.5" 256 x 64 gives more display area, (136 x 34), tho at a higher price of course.

https://www.aliexpress.com/item/1005006195056423.html