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General Chat / Re: Test Equipment Anonymous (TEA) group therapy thread
« Last post by xrunner on Today at 08:58:50 AM »
Yeah, it all sounds a bit fragile.

Ha! I just found another funny thing on this one, if you're interested I'll show you.  :palm:

Please say yes or I'll go nuts ...  :-DD

Beginners / Re: Can I blow the crap out of my scope if I probe this?
« Last post by Ian.M on Today at 08:51:08 AM »
No. 'Floating your scope' is generally a very bad idea. 

The front panel controls aren't designed to provide high voltage isolation, so even if it has a plastic case, it becomes hazardous to use.  If it has a metal case, and anything else on or near your bench is grounded, its a death-trap. 

Also its power supply insulation isn't  designed to 'stand off' more than the nominal supply voltage + a safety margin, so you risk blowing up the scope anyway, and probably doing a lot more damage than melting a probe wire that's the typical result of a ground clip mishap on a scope with robustly grounded input sockets.

Furthermore the large capacitance to true ground + noise injected by the scope PSU that normally gets shunted to ground will mess up any readings you take with the probe ground clip on a non-grounded point.
Beginners / High voltage supply
« Last post by neo on Today at 08:48:12 AM »
I need a high voltage supply and i have the good fortune to have a small transformer for old tube gear. It has 110 out which i then feed into the below circuit to get 220v nominal, since it is a cockroft walton the voltage drops to 170 with an approximation of the nixie current draw. Will this work in practice?

The worst case i can think of is one tube were to stop drawing current then the voltage would rise but from my calculations if one tube were to die the voltage would raise and so would the current and thus it would be relatively safe, correct?

Perhaps make the resistors have a maximum current draw equal to the maximum of the nixies so as to have a level of safety or maybe a glass fuse?
Beginners / Re: Can I blow the crap out of my scope if I probe this?
« Last post by tautech on Today at 08:47:47 AM »
Thanks, is it possible to buy some ac-ac transformer that will isolate my scope from ground? Or can i just cut the ground wire whilst I am probing? Will this eliminere the problem?

It's much safer to isolate the DUT from mains ground. Isolating a scope can elevate all metallic points and surfaces to the same as the DUT and expose a user to potentially fatal shocks.
General Chat / Re: LED bulbs experience? Do they last as declared?
« Last post by Red Squirrel on Today at 08:47:41 AM »
In theory CFLs and LEDs should last a long time, but normally they cheap out on the driver.

There is a lot of hate for CFLs but I have to say I have them throughout most of my house and they have lasted a long time.  I've had the odd ball go bad but a good part of them have been in use since I moved in a bit less than 10 years ago.

Back then the only LEDs you could get were spot lights and they were like 30 bucks a pop.  Now they make LEDs that are unidirectional like regular bulbs and they arn't that expensive so as the CFLs die I'll probably go LED.

For LED you really need to buy locally from a real store though. The stuff you get on Amazon comes straight from China with no UL rating and is going to burn your house down.  Some of them even have exposed mains.    That goes with a lot of stuff though, even phone chargers.  Lot of them arn't even mains isolated. So it's 5v out between the two pins, but it will be mains referenced and around 120v from pin to ground. 
Beginners / Re: Why so many ferrite beads in Meanwell AC/DC power brick ?
« Last post by Bud on Today at 08:41:16 AM »
Speaking of which, i've seen an application note, i believe one from ADI, saying running separate wires from analog AVDD and digital DVDD terminals on a PCB to a same power supply solves crosstalk problem AVDD to DVDD because of added wire inductance, so no additional board level measures are needed.

Edit: just remembered it was not an applicatioj note but a private email communication with an ADI engineer in regards to spurs attributed to powering a DDS analog and digital terminals from a same power supply.
Microcontrollers & FPGAs / Re: PIC32 now have a MMU...
« Last post by thm_w on Today at 08:40:56 AM »
Irrelevant specs, you will never use in iMX witout external DDR memory and Flash.

But its possible the PIC would be used without external flash or memory, no?
The point is its a different market, there is more on chip resources and the cost will be proportionally higher due to that.

1-2MB of flash on chip is not cheap, although I'm not sure if this is manufacturer set margin or actual cost of silicon. 2MB winbond flash is about 60c.
Beginners / Re: Broke pins off TO-220, solder new wires on ?
« Last post by RoGeorge on Today at 08:40:56 AM »
Sure you can. You can even decap a small region near the broken pin using a Dremel against the plastic case, in order to expose more metal for soldering.
The link is to see what is under the plastic case:
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