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Projects, Designs, and Technical Stuff / Re: super fast turn OFF Relay
« Last post by wraper on Today at 09:02:29 AM »
Just for information. I don't know if you are concerned about this but coil inductive kick suppression can significantly increase relay release time.
Some info to read if you don't know this already http://www.te.com/commerce/DocumentDelivery/DDEController?Action=srchrtrv&DocNm=13C3311_AppNote&DocType=CS&DocLang=EN
Of course that won't give you 100uS release time, but anyway.
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Blog Specific / Re: EEVblog #677 - Mailbag
« Last post by TEMProducts on Today at 09:01:52 AM »
Hello everyone! A few responses here...



Those power pegs are an interesting idea, I have never been a fan of multiple vias on a PCB installed underneath a chip in an attempt to promote heat flow. One thing though, with the power peg installed in the hole how do I solder the chip to the board/peg?

The pegs do not press fit. This would cause stress in the FR4. They slip-fit in a 2.5MM via.

Simply add a dab of flux, tack in place, allow to cool, and paste/reflow as usual. Action of capillarity holds the peg in place when the solder is molten.

I really like the Power Pegs, I will definitely have them in mind the next time I am considering though hole TO220s or similar with a standing heat-sink.

As I understand you screw the heat-sink into the peg after everything has been soldered. But since they are tiny, how much momentum can you use on the screw? How do you prevent the screw from shaking loose (Loctite?)?

1.0 inch pounds of torque MAX. Use a clutch driver, or screw by hand.

As long as the screw is fully engaged in the Peg, the screw will actually break before the thread strips. 0-80 screws are delicate!

PowerPeg is made of copper, so friction is enough to hold the screw in place when fully tightened. I have never seen one come loose (and I have used them in every way imaginable  ;) ). However loctite can be used, and does not effect the thermal interface.

Additional screws from PCB to heatsink are recommended to relieve mechanical stress from the thermal connector. PowerPeg is tough, but not invincible!

Those thermal pegs are quite nice, but one thing concerns me about them: Can the solder joints withstand the mechanical stress created by those pegs? Imagine you have 6-10 transistors on a board, all connected to the same heatsink, each with its own powerpeg. The heatsink will certainly have a different thermal expansion coefficient than FR4 - something will have to give.

The effects of thermal expansion of copper are negligible over short distances. For example: with a temperature change of 100C the length of the peg will change 0.000068 inches.

PowerPeg is precision machined to have matched thickness allowing many pegs to be attached to a single heatsink.

these Thermal Connectors are nice
but they are overpriced. $1.4 each ?? too expensive.

In the past two years we have made only one batch of 1200 pegs. The small quantity is the reason for the high price.

These pegs were hand made. They are precision  machined from copper alloy and plated with nickel, then 24 kt gold.

The next batch will be larger. I forsee the price under $0.80.
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Beginners / Re: looking for a bass amp for headphones
« Last post by EvilGeniusSkis on Today at 08:59:35 AM »
I think that your moding may have removed any stereo sound that the headphones had unless each slider had two variable resistors in it which I do not think it would have.
I put the volume slider on the ground side to solve that. I've found that setup in several different pairs of headphones.
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gradient on mine is always hotter bottom right hand
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Beginners / Re: Benefit of 3C-Silicon Carbide vs Silicon diode
« Last post by anandrmp on Today at 08:50:32 AM »
I have to illustrate the benefit via software simulation, not physical components (if that´s what you mean). Are comparable  3c-Sic models  available at Anvil?

You said that power factor correction would be the most appropriate circuit to show the advantages. Wouldn´t a rectifier circuit like the one i implemented, on its own, also show the benefits of using the silicon carbide diode?
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Other Equipment & Products / Re: Solder dispensers...
« Last post by dunkemhigh on Today at 08:48:06 AM »
I really really hate wires and solder wrapped around stuff on my bench, which is what tends to happen if you have a static holder and reel the stuff out. None of these stands has a rewind handle to reel the excess back in at the end, right?

A photo of my setup follows. The second shows it in use, comfortably fitting in my hand with fill control, and when I put it down the solder is off the bench (easy to use without a third hand when tinning) and stable. At the end it gets thrown back in the solder box (hence the slight damage).

Cheap too.
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The power-up continues...

 Checked the screen, grid and cathode voltages on the 6BG6 socket, and everything looked "safe. Hooked my scope to the grid, and got a reasonable-looking but low 30Vpp drive signal (service data says should be ~40 Vpp).  :-+ Things are looking pretty good, considering all the original paper caps are still in!

Shut down power, installed a 6BG6, and hung my DMM on the +225V rail. Made sure the 1B3 lead was in the clear, and applied power. Took a neon test probe (NE-2 bulb taped to a plastic stick), and held it near the 6BG6 plate cap. Bulb lit fairly strongly. Waving it near the 1B3 plate lead, it got much brighter.  Lots of high voltage RF being made.  No signs of arcing/corona/smoke from flyback.  Looking even better...

Stuck in a 1B3, and connected HV meter (Fluke 87 and 80K-40 HV probe) to CRT anode clip. Applied power and....whole lot of nothing.  About 4V if the meter can be trusted that low (.004 kV was the reading). Bringing back of hand near end of anode wire gave no static to hairs, and bringing a grounded screwdriver near it gave nothing at all. Bringing the screwdriver (now ungrounded) near the 1B3 plate cap (briefly) drew a 1/2" long RF arc. We have HV AC, but no DC.  :-// 

The 1B3 I have in it checks good (on a TV-10D/u) but it has a internal insulating coating that obscures the filament, so I can't see the filament glow.  Will have to dig up another one to try, I'm sure I have a few of them kicking around. 

Only other possibilities I see would be an open resistor under the 1B3 socket (R187 or R167) (somewhat common), or a shorted HV filter cap (C142, but these mica or ceramic "doorknob"caps are usually pretty reliable).

At this point, I'm going to go ahead and swap the 1B3 to rule it out, and then forge ahead on the recapping. Have all the needed caps ready to go in.   Would have liked to get some light on a CRT, but probably pushing my luck running this thing much at this point. The 1B3 socket resistors and the HV cap all require at least some disassembly of the HV cage to get at, so will investigate this area after doing all the underchassis work.




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Hi Elect0nicus,

I know this is an old topic, but I'dlike to know if you would eventually share your documentation about your charger?

Best regards.

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Quote
soft
Quote
no quiescent loss
Quote
immediately

Depending on how you define those terms, the answer ranges from "sure" to "no way".
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Projects, Designs, and Technical Stuff / super fast turn OFF Relay
« Last post by qwaarjet on Today at 08:36:40 AM »
I have an application where 15ohm resistive preload need to be disconcerted very fast when a parallel load is connected, currently my system is using a mechanical relay (400Vdc 15A)attached to my current sensor for the task. The current sense circuit responds in about 100uS but the relay take a little over 4mS to respond. The switching current is 10A DC. Looking around on digikey most SSR have turn off time greater than 1mS not very much faster than my mechanical relay, and most  device seems to be optimized for fast turn on instead of turn off. An SSR would be ideal so the switching element can float separately from the current sense circuit. I've used optical FET drivers in the past for switching floating loads but they are not very fast devices either. I would like to achieve turn off time on the order of 100s uS. Any suggestions on what product / architecture to use.

General requirements for the switch :
>10A
>180Vdc
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