Recent Posts

1

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

« Last post by xvr on Today at 12:10:07 pm »

Ok, lets start from NDT3055L

Calculate for worst case 2 amp in parallel with steady on state. We have 12A load.
Rdson = 0.1OHm, so Voltage Drop on transistor is 12*0.1 = 1.2V, This is 6% of 20V, this is more than 5% of amplifier tolerance (as far as I remember) - transistor can't be used in this configuration

Let's try to calculate for 6A load.
Voltage drop is 6*0.1=0.6V. This is 3%, so your power supply should provide 20V +5%/-2% (quite tight but possible).
Power dissipation on transistor: P = I*V = 6*0.6 = 3.6W. This is quite a lot for smd chip without heatsink.
Temperature raise: P*Tja = 3.6*42 = 151C. Die temperature is 151 + 25 (ambient) = 176C. This is more than 150C maximum. So, transistor can't be used.

Now, let's try to evaluate for pulsed mode (2s cycle 50% duty cycle). By Figure 11 give coefficient 0.5 to Tj.
So, Tja will be 21, Die temperature is 3.6*21+25 = 100.6. In limits, but still too hot. Each 10 degrees of temperature raise reduce life time of transistor by 2 times.
And relaying for pulsed mode also dangerous - if some amplifier will be turned on for more than some time (10-100s approximately) transistor will be burned out.

Now check SiSS65DN.
Rdson = 4.6mOhm. Voltage drop (12A load) is 12*4.6e-3 = 55mV. Almost negligible from point of view of power supply for Amplifier.
P = 12*55e-3 = 0.66W. Max T raise 0.66*25 = 16.5C. Quite cold.

PS. 25 is worst case for Tja (from datasheet). But it specified for mounting on PCB with 1" copper area and for pulse less than 10s. DS do not contain information for steady state. But there is a large reserve in power and temperature, so steady state should not be a problem.

2

General Technical Chat / Re: Relay trigger when voltage above 13v

« Last post by NiHaoMike on Today at 12:03:30 pm »

Use a supply voltage monitoring chip, it will already have many features you want such as hysteresis and deglitching.

3

Embedded Computing / Re: WINCE question

« Last post by Bicurico on Today at 12:02:55 pm »

I don't see any issue. This is the embedded forum and we are talking about WinCE, which is for embedded devices.

The fact that the binaries run on a PC with Windows is within topic, I would say

4

EEVblog Specific / Re: EEVblog 1612 - Siglent SDS1000X HD 12 bit Oscilloscope Teardown

« Last post by 2N3055 on Today at 12:01:27 pm »

Hi Dave, my 1204X-HD has microphonic inputs.

Wow. Why the difference?

Perhaps they forgot to mount the capacitors in your unit.
Let them know and they'll happily ship you a couple that you can solder in place...

It is because Dave used 50Ω termination....

It is amazing how easier is to just speak smack instead of looking into facts...

5

Power/Renewable Energy/EV's / Re: DIY Battery Bank from Recycled 18650

« Last post by mtwieg on Today at 12:01:14 pm »

What are those things in a glass package? Fuses?

I assume they're fuses. I'd like to ask them why they're only used on specific cells...

6

Projects, Designs, and Technical Stuff / Re: Homebrew Lock-In Amplifier

« Last post by Picuino on Today at 12:00:46 pm »

I don't really have much time right now. I am preparing the project for this summer when I will have enough time to assemble and test it.

I want to make a real LIA, which is fast enough to decode sounds in real time (10kHz minimum) from a higher frequency signal.

I don't care if it has a lot of quality, just enough for basic experiments to work. That's why I'm considering making the LIA with cheaper, simpler powered components (amplifiers). The problem is that I can't replace the AD630 with a simpler power supply. Sometimes I consider doing a digital LIA directly, but then I would not have any standard to compare.

7

Beginners / Re: Automatic golf ball dispenser

« Last post by BTO on Today at 11:59:52 am »

Ok guys, the final prototype.
https://youtube.com/shorts/KOmL9WKCEq0?si=T7d2N874ycgET7hB
It would have been nice in their forum if someone could have suggested ways to achieve this.

Also.. if you want us to have a look at your code, .... Post it

8

Beginners / Re: What size Teflon sleeve tubing are you using for 1/4 - 1/2 Watt Resistors

« Last post by RoGeorge on Today at 11:59:27 am »

You mean, like the green isolation in this pic?



Only rarely did that, and usually not with teflon tube, but with isolation leftovers after stripping casual wires.

9

Beginners / Re: Automatic golf ball dispenser

« Last post by BTO on Today at 11:58:51 am »

Ok guys, the final prototype.
https://youtube.com/shorts/KOmL9WKCEq0?si=T7d2N874ycgET7hB
It would have been nice in their forum if someone could have suggested ways to achieve this.

How do you mean ?  I mean, You're a newbie so i'll humour this .
But granted that a lot of people didn't respond but those that did did try to help , so.. what did you mean exactly ?
If however you meant that someone should have told you how to do it completely... NO, that's not the way it works.

Mate we derive pleasure from electronics, a large part of that is learning how to do stuff ourselves , therefore i we just said
do this and that and that and this and solder this to that and use this code.  You would literally have nothing to do .
We would feel that we deprived you of the pleasure of learning, which is also... the entire point of why i pushed you into the arduino and
ESP32 direction.

so. You are expected to pull your part of the weight as well, (and you did )
Now, you do have an option to ask us to do it all for you, but that would require payment , and that would give you the right to not
care how it's done and to have us just build it for you.

However most people here want to do it for free and to learn, I made the assumption that that's what you were after
so, I'm confused,   did you mean that you wanted to be told how to do it all upfront or did you mean you didn't get any support ?

or.. Did you mean that you wanted me to explain how that commentary DF Robot thing works   I didn't really understand your comment properly.

so i guess the question is...
WHAT HAVE YOU LEARNED SO FAR
AND WHAT DO YOU WANT EXPLAINED

10

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

« Last post by nctnico on Today at 11:58:48 am »

High speed camera and frame anlaysis is one way obviously.

If "screen update" means "pixels changed" (assuming a continuously changing input), then I think that's the only way

No need for a high speed camera though - you have full control of the source signal, so you can create test signals and use a simple single-point optical sensor on a specific area of the screen.

The more I think of it, the less I'm convinced this is actually easy to measure. In the end the rendering engine of an oscilloscope needs to pack multiple acquisitions into a rendered image which is not necessarily equal, but likely synchronised to the screen refresh rate to avoid tearing effects. If you look at the trigger output signalof an oscilloscope, you often see a whole bunch of triggers, dead time and another burst of triggers. The dead time is likely the time needed to create the rendering from (pre-processed) acquired data.