Recent Posts

1

Projects, Designs, and Technical Stuff / Re: Suggestions for secure authentication solution?

« Last post by mikeselectricstuff on Today at 11:45:40 am »

So basically you want a preshared key to make sure only official devices can pair and the during pairing create a new key just for the local security?

No, the key generation and sharing happens at the pairing process. prior to that, all hosts and nodes are "blank" and we don't need to care about them being "official"

How do you want to do the pairing? Button press on both devices?

The pairing process happens in a secure environment, so the nodes (and a new host) can initially be 'blank'.
The pairing process would be to connect a node to the host, and press a button on the host. The host would generate and store a random key, transfer it to the node and store it there ( or vice versa - doesn't matter). This key transfer does not need to be protected.

From then on, only that node will provide a correct response to a random challenge from the host, so if the node was disconnected, or swapped with another node, this can be detected. 

The requirement for the host to send a command to the node is a secondary requirement, and I think can probably be done by a reverse authentication initiated by the node.

Replay attacks are not an issue as the host will always issue a random challenge to the node.

2

Test Equipment / Re: SDS800X HD Wanted Features

« Last post by ebastler on Today at 11:44:47 am »

Improvement request: Remove redundant digits in axis labels

I have admitted to being a bit obsessive about axis labelling before... The Siglent software does a nice job in many respects -- it chooses consistent units and formatting along the whole axis, and lets me adjust vertical and horizontal offsets to "clean" round values via the encoders, so the labels become round numbers too.

But if I do so, I still get redundant trailing zeros on all the label values. In the attached screenshot, every axis label has two extra trailing zeros which could (and should, in my opinion) be omitted. That would reduce screen clutter and would make the label values easier to read -- both during live operation and in screenshots for documentation purposes.

Edit: Bonus points for adding a space in front of positive values on the Y axis, to make the decimal points of positive and negative numbers align. Did I mention that I am a bit obsessive in this area? 

3

Repair / SMPS repair - primary side controller not starting up/driving gate

« Last post by MateV on Today at 11:42:28 am »

Hello!

I've been trying to repair a blown SMPS, and got stuck.


The original fault seems to be Q9101(TK13A65U) going short, burning out R9101 in the process. C9104(OCP filtering) and R9108(gate resistor) were also bad, along with U9102(feedback optocoupler) having very low emitter-collector resistance.
Measured and replaced everything that was bad in this area, along with U9101.

Powering on the PSU results in the following on the Vcc pin of U9191:


There never seems to be any gate drive output, except a few picoseconds ~2V pulse, which I assume is just some sort of noise(no voltage detectable on any output on the transformer either).
Removing power from the PSU causes the following oscillation on Vcc until Vbus drops under ~20V:


U9101 looks to be this with a custom part number:
https://www.semicon.sanken-ele.co.jp/sk_content/ssc1s311a_ds_en.pdf

Full schematics:
https://elektrotanya.com/715g7831-p0e-000-0020_philips_psu.pdf/download.html

Any help or suggestions on what to measure would be greatly appreciated!
Thanks.

4

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

« Last post by egonotto on Today at 11:39:04 am »

Hello,

that is still 7 working days with today.
I hope they can keep to the announcement this time

Best regards
egonotto

5

Altium Designer / How to copy symbol and footprint from one component to another?

« Last post by thomasx on Today at 11:38:49 am »

Hi

I have a component, MOSFET transistor, that I want to place on the schematic. The component is found by the Manufacturer Parts Search, but there is no schematic symbol and no footprint.

Surely there is some way that I can easily copy symbol and footprint from another component that uses the same symbol and footprint into this one, how do I do that?

Thanks!

6

Test Equipment / Re: reading Keysight 3458A serial number

« Last post by analogRF on Today at 11:31:55 am »

This thread is continued in the eevblog Metrology forum

7

Repair / Re: SOLVED : Help with troubleshooting a Hypex SMPS400A400

« Last post by rfengg on Today at 11:28:47 am »

@fzabkar : Whoa....really surprised that the "RD" make is actually a Samwha.....being a S.Korean company didn't expect that they would be so pathetic, especially since Samsung uses a lot of these. No wonder that you cannot find Samwha at Mouser or Digikey.

@MathWizard : Have attached the data sheet of the Hypex SMPS400A400......no schematics in them obviously, but there is a "block" diagram which is quite useless.....but in fairness, the data sheet helped me find out the ouput voltages at the various connnectors.
BTW, the 8pin DIP is indeed a dual opto.

 SMPS400Axx0_15xx.pdf (976.81 kB - downloaded 0 times.)

8

Test Equipment / Re: Looking for a replacement general purpose oscilloscope for home use

« Last post by egonotto on Today at 11:28:15 am »

... With scopes up to 3000/5000 series Siglent IMO has had the time, has gained the experience, and has demonstrated the will to go "the extra mile", in short, became a mature player.
.....

Hello,

do I understand correctly that you consider the SDS3000X HD to be fully developed?

Best regards
egonotto

9

General Technical Chat / Re: Need 13Amp variac device to 'modulate' a water boiler.

« Last post by themadhippy on Today at 11:24:12 am »

If I simply take what I have now, the built in 3kw ring element in a "tea urn"

guess youve removed the stat from the urn,pity as they usually have a simmer setting.

The "Proper" and "Best" way I believe to solve this is

add a false bottom,grain basket ,ssr, pid and pump and make it into a   grainfather clone.

10

Beginners / audio amp study

« Last post by Herschel on Today at 11:20:57 am »

I am making a single supply audio amp according to this circuit. even though the amp is biased by two diodes, here i used 1n4148 and a 22R resistor, why is this 200k potentiomete for? is it to control the output of the amp? not sure...
also the website dosent say anything about it.

https://www.eleccircuit.com/50-watt-audio-amplifier-circuit-with-pcb-using-2n3055/