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Author Topic: Your latest purchase  (Read 76746 times)
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Trolling... as small kids smiley

So, here is the factory page:
http://www.manson.com.hk/products/detail/18

And chapter IX. Specification says:
Over Voltage Protection (Main Output): 18~22% at tracking 10.1V <Vout ≤19V

I have no idea what this mean, but there is an undeniable existence of value "19V" and maybe it's a relationship.
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Arduino Uno R3, Arduino Mega 2560 R3, Ethermega (R3), and some Ethernet Shields (R3), Chronodots, TMP36 sensors, DS18B20 sensors, LCDs/TFTs, RS232C to learn and play...

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One thing to know about bench supplies like this is that they can't always supply max amps especially when using outputs as low as for example 1 vdc. A linear regulator can exceed it's maximum heat dissipation before reaching it's maximum output current rating due to the extremely large voltage drop across the regulator when set to lower output voltages.
I've seen some complex designs that lowers the unregulated voltage input to the linear regulator as one lowers the desired output voltage to keep within heat dissipation rating. Only a schematic drawing would tell if there is anything like that used in this unit, but perhaps the owners manual covers the issue?

Back in the 80s we used H.P. bench supplies like this (except metered not digital displays) that would cost around $1,500 or better depending on options. They were bullet proof quality and were hard for even a beginner to damage.

Lefty

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A 5A linear supply?  Wow, I wouldn't have guessed that.
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5A linear, aka boat anchor as the EE's who taught me "go for smoke" called them at fests.

I've been wondering if something would work. I have 9V supplies that if I put a 7.5V zener and a good bit of resistor across +9 and GND, would I get 7.5V to a 5V regulator without wasting much power? I am guessing that the resistor would share the heat of 9V down to 5V with the regulator but how to figure the resistor value?

Does that even make sense?
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Examples can be found in your IDE.

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Using a resistor in series with a Zener is a common way to get a voltage reference, but it's of limited value as a regulator.  Basically the current draw has to be exceedingly small, because as you pull variable current from the supply, there will be a corresponding voltage drop.  If you follow this with a traditional linear regulator, sourced from the junction between R1 and D1, the regulator will drop the remaining voltage.  This could be anywhere from the entire voltage difference (at no load) to being already well below the desired regulated voltage (at heavy loads).  If you calculate the max allowable current draw and size the resistor so this load corresponds to the point where its voltage drop results in a perfect Vin for the linear regulator, you can probably make it work, but it's a kludge.

In addition to being dependent on current, using a resistor is not at all an efficient way to drop voltage -- it becomes wasted heat.  However, it's essentially how all linear regulators work (except the resistance is variable depending on the load) and also what makes linear regulators inherently inefficient.

None of that really takes the Zener into much consideration.  For that, you have competing goals:  Keep the resistance high to avoid dumping tons of current through the Zener, which would overheat it and burn it out; and keep the resistance low so you can draw current from the PSU without simultaneously dropping all available voltage through the resistor.  There's a fairly small window where you can satisfy both criteria.

Your line of thinking is how to reduce the heat load on one regulator, correct?.  The simple solution to this is to spread that load among other devices.  One such way is to use a regulator as a controller, and have the load pass through a heftier transistor (and/or parallel transistors).  You can also pre-regulate the voltage so the drop is shared between two or more regulators.  This works, but it's usually not the best approach.
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Would an LM317 get around all that? I think I have however many a dollar or two cost from where I fleshed out an order with cheap, interesting-looking parts to justify shipping... in one of my past purchases (back OT?).
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Examples can be found in your IDE.

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No, an LM317 is still a linear regulator -- it's just designed to output an adjustable voltage.  You can force a 78xx or 79xx to change their regulated voltage too, if you step outside the typical application design in the data sheet.

Many of the linear regulator datasheets do include schematics for using external transistors though.  Then you're designing a linear regulator that has much in common with a Class B power amplifier, with the same flaws... namely, that Class D amps and switching regulators can be much more efficient for high-current loads, at the expense of being more complicated and not as well behaved if poorly designed or poorly matched to the load.
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Air, and some RGB LEDs for my Mood Light (look meh up on Instructables)
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 A 99 cent, 12vdc @ 2 amp switching regulated wall transformer with 10 foot cable with standard arduino like connector at a local charity store. Can't have too many of these.

Lefty
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2mm & 5mm heat shrink cable.
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Hi, just used my work bonus to goto Bunnings (DIY) to get materials to build proper shelving to sit on work bench.
Hope to get LED string under lower shelf to light bench area and hooks and bars on side to fasten clip leads, gluegun and heatgun.
Also want to run leads from LAB supply to a series of terminals along front of shelf, sick and tired of banana plug on banana plug on banana plug etc etc..to get juice from supply and provide gnd ref for  test gear.
Have made design so as little timber cutting as possible.
Will let you know how I go.

Tom..... smiley  (damn forgot to check if drill is charged..) Have circular saw will attempt carpentry.
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A bunch of LEDs in jolly colors from evilbay.

I'm a sucker for LEDs.......they are just so pretty! They shine, they smile to me, they illuminate me!

(or maybe it is just the memories of the anemic green and red LEDs of the late seventies and eighties?)
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Quote from: TomGeorge
..to build proper shelving to sit on work bench.

You know this calls for a picture after completing this, don't you ?
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Have a look at "blink without delay".
Did you connect the grounds ?
Je kunt hier ook in het Nederlands terecht: http://arduino.cc/forum/index.php/board,77.0.html

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I was thinking the same thing.  Maybe someone should start a "show off your cool work bench" thread.  I could use some inspiration.

(My work bench is the shield plate from an old LCD monitor, sitting on one of the three unoccupied square feet of floor in my spare room.  But some day...)
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Ordered the laser cut parts for the uFactory robot arm....
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Have you looked for answers in the Learning, Reference, Products and Playground tabs on http://arduino.cc/en/ ?
Look here http://electronicsclub.info/ for basic electronics

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