Recent Posts

1

Projects, Designs, and Technical Stuff / Re: Accurate sine wave in terms of amplitude

« Last post by Terry Bites on Today at 03:39:24 pm »

That DDS chip has an output stabilty quoted as "200  ppm/°C" not great, but then DDS is aimed at RF where no one cares much about precise amplitudes.

DIY your own DDS:

Back in the day, before low cost microcontroller platforms and social media had been dreamt of, I made a sine source for an LVDT sensor using a lookup table on a M27C1024 eprom (still to be found on ebay and in my 90's junk box), some counters (74LS590 i think) and an AD669 (still available) with a REF01 10v reference. That was 16 bits of rock solid 10v pp waveform! No control loop rubbish to worry about. For your puposes a very simple antialias filter is needed to polish off any clock residues. Of course you can easily tune it up using the counter's clocks. Add your own precsion attenuators and gain. Feels good.... 

I think a pwm source driven by code or from a lookup table could do just as well. Precision clamp the PWM amplitude, nice lowpass filter, job done. The Arduio can create 16 bit PWM using its internal timers. Sine dump here www.daycounter.com/Calculators/Sine-Generator-Calculator.phtml

2

Test Equipment / Re: SDS800X HD Wanted Features

« Last post by mawyatt on Today at 03:38:14 pm »

Can one imagine what we would end up with if all the wants, don't likes, stuff this and that in, make it do this and that, and so on, would create?  Designed by Committee seems to fit, but Complete Cluster F**K seems better

The old HP and Tektronix didn't yield to all this type of BS, they had a group of knowledgable engineers/scientist, were actual in-house users, that decided how the instrument would be configured and built.

If a potential user didn't like what HP and Tek offered, wanted this and that, tuff then user could go somewhere else, or fly a kite!! We the users learned to use and operate the HP and Tek equipment like it was intended for, and generally for the better!!

Why, simply because HP and Tek engineers were more knowledgeable about their own instruments than any users, and we the end users learned and benefited from these Masters. Folks that didn't learn from this user experience unfortunately ended up being managers/excutives, and later this trickled up into HP and Tek pyramid which lead to their own demise

Hopefully Siglent will have limited BW and only listen to the very few knowledgable folks, which we know who they are!!

Best,   

3

Other Equipment & Products / Re: Lets see your Nixie Tube equipment

« Last post by Dave Wise on Today at 03:38:11 pm »

My Monsanto model 2000 Digital Voltmeter.  DC Volts only.  Easy on the eyes 20000-count non-multiplexed display required many many RTL integrated circuits for counters and latches.  As far as I can tell, this is Monsanto's only DVM ever.  I never found any advertisements for it, just an oblique mention of "a digital voltmeter" in an article from Chemical Engineering News January 1966 edition... which I can't find anymore.  Gift from the late noted Tektronix collector Stan Griffiths.

It uses a single-slope converter with an electromechanical "Synchroverter" chopper.  Communication across Guard is two pulse transformers with interesting signal timing.  The automatic polarity switching is awkward and went through significant mods that appear to be from the factory, and it was still flawed - to measure a guarded negative voltage you had to manually connect GUARD to the IN terminal instead of the COMMON terminal.  I fixed that by changing the circuit yet again.  Other changes I made ended up inserting two microcontrollers to correct some timing glitches.  It's kind of a Frankenstein but it works.

4

Repair / Re: Laser Level Charger PCB ID

« Last post by Shaky on Today at 03:36:24 pm »

Well, all I can say is WOW ! Thanks for the comprehensive reply @globoy but unfortunately, it looks like repair is way above my pay grade 

All I have available to me is a mid-range digi multimeter, no scopes or anything like that. It was basically an attempt at trying to save a mate (who doesn't do anything electrical at all, let alone electronics) a few quid 

If it helps, the wall-wart outputs 5v, the battery is showing 3.6v but there is 0 volts on the + & - brass pins on the pack. Funnily enough, there is 3.6v between the - & the Y pin, which made me think it was just a simple charger/bms.

Ah well, I'll let him know that he'll have to wait for the packs to come back in stock.

Thanks again for the reply, it's appreciated.

5

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

« Last post by Fungus on Today at 03:33:43 pm »

Simply put, Rigol hit a Home Run with the DHO800 introduction, then Siglent hit a Grand Slam with the SDS800 introduction 

Yep, there's no way the Siglent boys will ever make me regret buying mine or that it's in any way insufficient for my work.

As good as the Rigol DHO800 is, and it's good, really good is every aspect, the Siglent SDS800 is just overall better IMO.

On paper, sure, but my question is how much of that translates into an advantage in practice.

Sure, there's some people who need 4 channels at 200Mhz over 50 Ohm coax that but I'm not buying that every single EEVBLOG member does.

I'm also not buying that those people wouldn't be far better off with a 2000-series 'scope at 350MHz. which seems to be an area where Siglent is supreme. "200Mhz" seems like a very arbitrary number to me.

So let's list the advantages of each and not try to say one is "better". Numbers aren't everything, one size doesn't fit all.

So when we reach for a DSO, now we reach for the SDS800, usually with the Rigol probes tho (these are really good, better than the Siglent IMO) 

Rigol has their own ASICS so Siglent's margins are probably a lot thinner to be able to be sell at the same price point. Things like the probes will be the first to suffer.

6

Test Equipment / Re: Enabling options on Agilent ESA series E4402B E4404B E4405B E4407B

« Last post by Larry_Bridge on Today at 03:30:31 pm »

Thank you very much.
I will check and let you know.

7

Beginners / Re: How Current Limitation is happening in the circuit???

« Last post by ommsiva on Today at 03:29:16 pm »

Mam,

Sorry,   absolutely you are correct.  It's my mistake, each picture were nearly 6mb and our site allows maximum of 8mb totally for a reply.so i reduced the image size .Now I have disconnected power transistor from heat sink out of frustration.

8

Projects, Designs, and Technical Stuff / Re: a high side load switch made from n channel and p channel mosfet working princip

« Last post by Doctorandus_P on Today at 03:27:41 pm »

Yes that is a possibility, myne had to work from 12V to 50V, so that made it a little more complex.

Benno

Meh, replace R2a in the previous schematic with a TVS diode, or better, add a TVS diode to limit the maximum gate voltage, but leave  the resistor so it will firmly turn the FET off when it should be off.

Circuits like this switch quite slowly, because of the combination of resistors with the gate capacitance. This is OK for switching loads occasionally (such as also done with Relays), but if you want to switch loads fast (such as with PWM) then this slow switching may cause a lot of trouble and the FET is likely to let out it's magic smoke and die in a puff or a loud bang.

9

Microcontrollers / Re: primitive serial CLI / Console for embedded systems - Ideas for implementation?

« Last post by Warhawk on Today at 03:21:58 pm »

And one extra question.
Does it make sense to optimize the CLI for VT100/Putty/miniterm type of communication (each character transmits immediately after the keypress) or for terminals that "wait for enter" (e.g. Termite) and send the whole line?

10

Microcontrollers / Re: primitive serial CLI / Console for embedded systems - Ideas for implementation?

« Last post by nctnico on Today at 03:21:30 pm »

Unfortunately no code to share. But what you need is a function which replaces spaces by 0x0 and puts a pointer to the beginning of each parameter in an array and keep track of the number of parameters found. Then a for loop which iterates through the list with commands and comparing each command to the first element of the parameter found.