What type of lasers? CO2?

Neon, I think. The laser part was all self contained. A glass tube with the mirrors and an arc to illuminate the gas. What I worked on was the self leveling and angle adjustment circuits. Plunk it on the floor, flip the switch, and it would self level then use a mirror on a motor to spin a horizontal beam around the room. Don't want horizontal? Dial in the angle you want and it adjusts to that angle.

Well if you feel that way you have to follow some straitjacket means if there's a protection feature built into the IC you have to use this by all means?

It had nothing to do with how I feel. The specs on the power supply had to be met, and the BSEE design wouldn't meet specs.

ps, I don't like the design in post #20 because the ground leg current changes by 8% as the load changes from 5ma to 1 amp. Of course, you are free to determine if the two chips track each other sufficiently for your purposes.

 

This looks like another overly engineered just because theory suggests it may have an issue circuits.

Personally I have used multiple voltage regulator IC's inparallel many times with nothing more than a few .1 uF capacitors close to their inputs and outputs to keep them stable.

The thing is, so what if one runs a few mV higher than the rest, when it's current limit is reached it's output voltage drops so the IC with the next lower voltage output will start taking over on supplying additional current and so on.

 

View attachment 113784


How about making the regulators adjustable by a volt or so?

A bit creepy since the diodes will not just drop 0.7V
Depending on the current it could be 0.6v to 0.9v

Sure this will all work somehow its possible to make a switching regulator with these IC makes hissing clicking and whining noises.

In the 1970s they had large linear regulators same encasing as 2n3055 with cooler.
Ive disassembled a 2n3055 PCB some day capacitor SIEMENS 1000uF from 1980 still working and giving good sparks. The 2n3055 needs decent Amperage to fry up just, no chance with a small wall adapter.

 

Output voltages are

1.8v
3.3v
5v

Cost is very little the DVD kinds can be had for less than USD 3 incl a small cardboard box since they are mass produced theyre cheap.

You would not normally connect two in parallel.

If you study the internal schematic of the 7805 you can eventually find some answers yourself.
The 78L05 is OK to use for small current when I was young I remember I fried up several 7805 they turned very hot and then didnt work anymore.

So they have some protection but not good enough against someone like me in young age.

 

If you study the internal schematic of the 7805 you can eventually find some answers yourself.

Yes, I've been thinking about that ... but it would be a very time consuming (although also fun) task ...
I wonder if anyone has posted a complete LTspice sim of the innards of a 7805 before ... gonna Google it up. Maybe I'll find something interesting.

Thanks!

 

What I worked on was the self leveling and angle adjustment circuits.

What technique did you use to accomplish that? I mean, there were no accelerometer IC chips back then, were there?

 

What technique did you use to accomplish that

Start with 2 slightly curved glass vials containing liquid and a bubble. Sense the bubble.
1) Analog circuits try to find zero by turning a stepper motor.
2) When the bubbles are zeroed, the mirror table is level north to south and east to west, therefore the entire circle is level.
The laser and the mirror are mounted on the table.
3) Spin the mirror.
4) Want a different angle?
5) Mount the bubbles on a rack and tilt the rack opposite the way you want the angle.
This is only a mechanical function done with gears and a knob with numbers.
Resolution to 1 degree, accurate to 1/4 inch at 100 feet.
That was 1975 and $6000 each.

 

Looks like it has .25 ohms in series for the newer ones. .3 for the older ones.
The initial tolerance is +/- .1 volt @25C, .2 volts at temperature.
So it would take .8 amps before the second one would try to help - not so good. I'm not sure the .1 is enough for worst case either.
Edit:
They make bigger ones you know.

 

How about this ?

 

Hello,

Better use a big PNP pass transistor as in the following circuits:





Bertus

 

How about this ?
View attachment 113796

That's more or less the same circuit as in post #1, except that yours uses independent diodes for the 7805s ground pins.

 

You could try it.

 

Looks like it

only the R21 is something thermistor or alike
they note about at the end of the src

 

only the R21 is something thermistor or alike
they note about at the end of the src

What page?

 

96
(but it might've been a different doc coz i remember N-supplies in parallel ... if i mind to dig for it soon enough)

 

96
(but it might've been a different doc coz i remember N-supplies in parallel ... if i mind to dig for it soon enough)

Ahh yes, I see.
It would get pretty complicated with a 7805. You would need a negative supply in case the tolerance was in that direction.

 

This thread is becoming far more interesting than I thought it would.

Good learning here...

 

This thread is becoming far more interesting than I thought it would.

Good learning here...

If you put them in parallel without a buffer resistor, one will automatically be higher than the rest and will be the first to go into protection mode when it overheats (or over current). At that point all others will cascade into protection mode because the next highest one will carry the biggest cross and collapse (with its big brother already in protection mode so he will go into coma state faster.

Anyhow, if you look at the peak current expected, divide by number of LM7805 to get the desired average of each, then measure the range of voltages that each of your LM7805 regulate to at that load. Let's say you'll use 5 X LM7805 in parallel and expect 0.5A each part (2.5 A total) and the parts output voltages of 4.95 to 5.05V.

Then then pick an output voltage slightly lower than your lowest regulator, 4.85V. Add a resistor directly to the output of each regulator at the targeted 0.5A to drop the regulator to the targeted voltage using ohms law. That is, the 4.95V regulator gets a 0.1V/0.5A = 0.2 ohm and the 5.05V regulator gets 0.2V/0.5A = 0.4 ohm.

All will be right with the world.

 

All will be right with the world.

Amen to that ... seriously, thanks!

 

At that point all others will cascade into protection mode because the next highest one will carry the biggest cross and collapse (with its big brother already in protection mode so he will go into coma state faster.

Doctor Gopher took charge as I can see.

Interesting thread.