Dropping 1V from a Regulated 6V Wall Wart

Hmm, a complementary-darlington emitter-follower transistor would be less sensitive to changes in load current:

: +6.0V, from wall wart : >--+--------+------+ : | | | : | 220 | Q1 2sa1011 : | | |/E pnp TIP32 : | +----| etc : | | |\ : 1.0k |/ | : pot + output : | to load : - >--+---------------------> -

Here the Q2 voltage drop is much more predictable, because it has a relatively steady current set by Q1's base-emitter resistor, which has about 0.55 to 0.75V across it despite output load changes. The Q2 current is about 3 - 5mA and we expect a Vbe drop of about 700mV. The lower end of the pot sits at about 5.3 volts.

The most serious problem with this circuit is its complete reliance on a possibly-uncertain input voltage; the output will track any changes in input.

snipped-for-privacy@nospam.com analyzed Watson A. Name's circuit:

Watson A.Name - Watt Sun, Dark Remover asked:

No, it's an ordinary regulator, using Q2's Vbe (roughly 0.7V) as a voltage reference. The pot as shown would be a poor choice because valid adjustments would only use a small part of the pot's range. No doubt nospam knew that and was just simplifying his drawing by using one part instead of three. This should work; the top of the pot has about 0.82V when the regulator is calibrated for 5V out:

This circuit has several problems. The tempco of Vbe is bad, but the uncertain current through Q2 an even worse problem. This is because the voltage difference between the +6V input and Q1's base is small (and may vary widely), and Q1's base current is unknown. If Q2's current changes by a factor of 10, its Vbe will change by about 60mV, or nearly 10% of its value. As a result Q2 makes a poor voltage reference in this circuit, even if manually adjusted.

A big cap is fine, maybe even necessary in that location, because a small output cap could make the feedback loop unstable. We discuss this issue in AoE and call it brute-force compensation.

The current w>

This is a much better approach, using TL430's 2.75V reference with a built-in error amplifier. The more popular TL431 can be used with its 2.50V ref if the feedback-sensing resistors are the same value.

But I'm not happy with the output emitter follower in the circuits above, because the low Vin - Vout difference leads to such widely- varying currents through the control element. Perhaps my circuit can be combined with Jim's circuit:

: +6.0V, from wall wart : >--+------+------+ : | | | : | 220 | Q1 2sa1011 : | | |/E pnp TIP32 : 750 +----| etc : | | |\ : | |/ | : +----| Q2 | : | |\E npn | : | | | : | +---+--+----> + output

Thanks, - Win

whill_at_picovolt-dot-com

Reply to
Winfield Hill
Loading thread data ...

I'm still not happy with the poor dropout-voltage capability of this circuit. It should be able to operate with Vin much closer to Vout. Aha! Simply adding a diode and resistor lets us reduce the dropout voltage down to near the saturation voltage of Q1.

: +5.3 to 9V : >--+-----+------, SIMPLE 5.0V REGULATOR : | | | : | 220 | Q1 2sa1011 : | | |/E pnp TIP32 : 470 o----| etc : | | |\ : | |/ | : o---| Q2 '----o----> +5.0V : | |\E npn | output : | | | to load : | | 1n4148 | : | '--o--| | | |

Of course, an even more simple circuit is possible, using one of the many low-cost low-dropout three-terminal regulator ICs.

: +5.3 to 9V etc : >-------, EVEN MORE SIMPLE 5.0V REGULATOR : __|__ : | | : | |---+---> +5.0V : |_____| _|_ output : | --- to load : | | : - >-------o------o---> -

But this circuit isn't as much fun. :>)

Thanks, - Win

whill_at_picovolt-dot-com

Reply to
Winfield Hill

In article , snipped-for-privacy@jmwa.demon.contraspam.yuk mentioned...

This alt 0233 --> é looks to me like it's an accented e, as in Jose' What's it look like to you?

--
@@F@r@o@m@@O@r@a@n@g@e@@C@o@u@n@t@y@,@@C@a@l@,@@w@h@e@r@e@@
###Got a Question about ELECTRONICS?   Check HERE First:###
 Click to see the full signature
Reply to
Watson A.Name - "Watt Sun, Dar

An e with a single dot over it, not the accent mark as in Jose'. I think it's one of those pronunciation symbols.

--
Best Regards,
Mike
Reply to
Active8

It looks (the outer part) exactly like one of those RS push on F connectors - the male one (male center conductor, female housing) but the center conductor is hollow and split as if the mating connector would compress it and cause it to seize the mating connector's center conductor which in that case would make the CIQ (connector in question) female and female no thread. I couldn't quite get a real idea of the size from the photo. Let's check Pasternack.

The PAL connector in this book is a push on, but the CIQ can't be this PAL connector. The one I'm looking at is male-female into female-male with the male housing (which would correspond to the CIQ) is .370" OD.

I see 75 ohm MCX connectors where the jack corresponding to the CIQ accepts a plug with a .147" OD housing - seisure and all.

I'd replace the friggin' thing with something I can lay hands on easily. F connectors are common enough. Push ons I only use for testing.

--
Best Regards,
Mike
Reply to
Active8

Now, did you do this years ago and just walk through the thought process for the benefit of the group, kinda like the "Now Read This Article and Burn it." article, pulling a rabbit out of your hat to the awe of the crowd? :) or what?

Happy New Year and best of health.

Mike

--
Best Regards,
Mike
Reply to
Active8

If you want a 1V drop (for some reason???) then something like this:

Please view in a fixed-width font such as Courier.

LM185-ADJ \ +---------|< |---------+ | \ | | | +------+-------------------------+ | | | | | / | | | 470 | | | / | | | TIP42 \ | | Vin----+-------- e c ---+-------+----------------------->Vout | \ / | | | | --- | | c | 10K | 1N4148 | | 10K |/ +----/\/\---+---|>|----+ +--/\/\-----+---| | | |\ | c e | \| | | |---+ | /| | / e / 470 | 1.3K / | / \ | \ | | | --- --- ---

Reply to
Fred Bloggs

I read in sci.electronics.design that Active8 wrote (in ) about 'Dropping 1V from a Regulated 6V Wall Wart', on Thu, 1 Jan 2004:

The dot instead of a proper accent is a feature of whatever font you are using. Look at it in Courier, Arial, Times New Roman.

--
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk 
Interested in professional sound reinforcement and distribution? Then go to 
 Click to see the full signature
Reply to
John Woodgate

I read in sci.electronics.design that Active8 wrote (in ) about 'Dropping 1V from a Regulated 6V Wall Wart', on Thu, 1 Jan 2004:

You've described a Belling coax connector, I think. I don't know what Pasternack is; a connector distributor?

I just don't recognize the term 'PAL connector'.

You should be able to get Belling-type connectors from Farnell/Newark.

--
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk 
Interested in professional sound reinforcement and distribution? Then go to 
 Click to see the full signature
Reply to
John Woodgate

Uh, sorry. It's pretty much the same in all three. The problem is, at this high screen res it looks like a dot when in fact it's a small slash.

Hey. If you ever have that prob (I use high res to make room for large CADs so other apps without zoom are screwed) there a little toy called Screen Loupe you can get. It's like having a magnifying glass you can drag around the screen like a sceen color picker or screen tape measure. Glad I remembered.

--
Best Regards,
Mike
Reply to
Active8

------------------------ Hey Watson. You accidentally typed alt 0233 as you said instead of alt 0223 like John said :)

Also, measure your connector & see if that MX 75 O [

Reply to
Active8

Yes.

formatting link
It seems like they replace my catalog every month. They have a UK disty:
formatting link

I thought PAL was/is (it is) a Europeeeen video standard. But there is a PAL connector in the cat sure enough and it ain't what Watson's got.

----------------------

----------------------

That's a good source for a lot of stuff. In Baltimore there's Bainsville Electronics which is great, but I've only seen gold- plated *kits* in the showcase. I'd wager they have it though.

>
--
Best Regards,
Mike
Reply to
Active8

My mistake. I read the subject line and the first line of the post and mistakenly concluded that you wanted to use a regulated wall wart. My baad. mike

Reply to
mike

I read in sci.electronics.design that Active8 wrote (in ) about 'Dropping 1V from a Regulated 6V Wall Wart', on Thu, 1 Jan 2004:

Indeed it is; it's the whole phrase 'PAL connector' that I don't recognize.

--
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk 
Interested in professional sound reinforcement and distribution? Then go to 
 Click to see the full signature
Reply to
John Woodgate

Hmm. When I hit alt-0233, I get one of these: !

Cheers! Rich

Reply to
Rich Grise

I can say with cetainty that I received an exclaimation point.

Hopeless?

Maybe not. If what I received is what you sent then the same code is displaying the same character on the screen on both ends. JW and I seem to have the same settings (odd because he said he used winders 98), but you either have your locale set differently or something I haven't though of.

I'm set for English(United State) - Regional and Language settings in control panel.

Character map isn't working here for omega so I'd better blow it off.

--
Best Regards,
Mike
Reply to
Active8

alt-0233 = é with NumLock ON or OFF, Win2K machine

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
 Click to see the full signature
Reply to
Jim Thompson

Don't type the leading zero unless it's a 2 digit code, ASCII codes are all

3 digit from 000 to 255.
Reply to
James Sweet

In article , snipped-for-privacy@neti.saber.net mentioned... [snip]

Yeah, but I've got four or five of them and I didn't want to crack them open and then have to deal with the hassles of a case that's no longer solidly sealed. And besides, they were only two bucks apiece. I may bave paid more for their shipping.

Also, I bot four of the 6VDC unregulated wall warts at the same time, and they have about 7 or 8V output unloaded. I don't think they have enough voltage to allow a 7805 to work properly, at least not up to

200 mA, because the DC voltage drops down to near 6V at that current.

But 6VDC is a convenient value, used by a lot of equipment that has four AA cells. So I have them just in case I want to 'electrify' one of those ol' radios or whatever.

--
@@F@r@o@m@@O@r@a@n@g@e@@C@o@u@n@t@y@,@@C@a@l@,@@w@h@e@r@e@@
###Got a Question about ELECTRONICS?   Check HERE First:###
 Click to see the full signature
Reply to
Watson A.Name - "Watt Sun, Dar

In article , snipped-for-privacy@jmwa.demon.contraspam.yuk mentioned...

Yeah, but here in the U.S. you go to Rat Shack and buy a Euro or PAL adapter, shove it in the socket, and forget about it for the rest of the life of the equipment. Everything else is done with F connectors, so it's not really an issue. In fact, I may heat up my big 100W soldering iron and make the adapter a permanent part of the equipment. ;-)

--
@@F@r@o@m@@O@r@a@n@g@e@@C@o@u@n@t@y@,@@C@a@l@,@@w@h@e@r@e@@
###Got a Question about ELECTRONICS?   Check HERE First:###
 Click to see the full signature
Reply to
Watson A.Name - "Watt Sun, Dar

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.