Testing DDl's circuit

I am about to post a "How To" on testing DDL's circuit before adding the LD, I hope it is all pretty clear and with no errors. Those members who have been there, done that, would you please let me know if you disagree with anything therein.

Regards rog8811
*Edit Circuit layout attached to help with circuit testing

I have seen so many threads recently posing questions on the expected output of DDL's circuit.

I thought maybe a picture would paint a thousand words

Things to check before you start testing

1) Is it wired correctly?

2) Is there enough voltage? (Rule of thumb 6v for reds 9v for blue)

3) If supply is via batteries, are they fresh? (Used ones may sag and effect your measurements)

Now to test it out......

4) Attach the 4 diodes and resistor to where LD will eventually connect. If your reverse diode and capacitor are already connected to your LD you can connect your test assembly to the output from your fixed resistor and the neg of the battery.

5) Turn the pot to maximum resistance (then back off the pot a turn if it is a 25 turn one to ensure the wiper is not right on the end of the resistor track)

6) With your DVM set to volts attach red and black leads as shown at either end of the diodes. Turn on supply, now wind your pot right up to see if the voltage doesn't exceed your required voltage.

7) Turn off the supply, change range on DVM to mv and attach red and black as shown either end of resistor. Turn on supply and the mv reading will be equal to the maximum milliamps that your LD would see, now wind the pot resistance up to check that the reading reduces smoothly down to the lowest mw, which equals the lowest ma your LD will see.

8) You can also connect your DVM, set to volts across the Vout and Vadj pins of the regulator, you should read 1.25v (thanks rckstr)

9) If all seems OK leave the pot at max resistance, disconnect the supply and remove your test assembly.

10) VERY IMPORTANT! If your capacitor is not connected directly to your diode (in other words it is already in the circuit with your regulator) you MUST short out the + and - at the output with a piece of wire to discharge the capacitor. Failure to do so will blow your LD as you connect it up!

The rest of the set up is up to you, the above only checks that the circuit works correctly.


Regards rog8811

Oops... realized this isn't the place to post problems, you're just asking if it sounds good....

It does to me... didn't see any errors.

Also may mention to measure the voltage between the Vout and Vadj pin to measure reference voltage to see if your supply is adequate.

omg! thanks you soo much!!! I'm finally figuring this crap out, lol, thanks!

now if only someone would do the same thing using the 7805 regulator!!!! gotta find something to with these things I bought!

I set my 7805 circuit up in exactly the same way, excluding the ref v measurment.

The thing to remember is that 7805 must be configured as constant voltage not CC and needs around 7.2v input to drive a blue ray.

I have not tried it for red LD's as I feel there is no point when the LM317 does it so well.

Regards rog8811
[edit]Years later.... test load schematic added[/edit]

isn't that dummy load designed to best match the red diode?

would I just have to add a few more 1N4001s to make it like a bluray?

member02 said:

isn't that dummy load designed to best match the red diode?

would I just have to add a few more 1N4001s to make it like a bluray?

Click to expand...

A good dummy load for a BluRay seems to be 4 green LEDs in a 2x2 parallel-series config.


_______/----LED----LED----\_________
\----LED----LED----/

(`')
I \/ ASCII art

You could also use a 1/4Watt 100 ohm resistor for a BluRay dummy load. It is fairly close to the dynamic resistance of the BluRay when running at around 40-50mA. You can also calculate the current in your head by measuring the voltage and dividing by 100.

This helped me.

A lot.

I'm rebuilding mine, and well see how it turns out.

Thanks for the additional input guys, as long as the good stuff is located on page one it may remain a useful thread.

To those for whom this is helpful with their projects, I am glad to have been of assistance.



Regards rog8811

rog8811 said:

Thanks for the additional input guys, as long as the good stuff is located on page one it may remain a useful thread.

To those for whom this is helpful with their projects, I am glad to have been of assistance.



Regards rog8811

Click to expand...

Good stuff Rog! You know I will be marking this thread. Thanks for doing this...
Jay

rog8811 said:

Thanks for the additional input guys, as long as the good stuff is located on page one it may remain a useful thread.

To those for whom this is helpful with their projects, I am glad to have been of assistance.



Regards rog8811

Click to expand...

Good info Rog8811. I wish I had found this info before I spent a bunch of time chasing my tail. Luckily you and some others responded in a thread I made.

Excellent!

Yet another great write-up by Rog

Hopefully once I get away from all the GB's (soon), I'll be contributing some more as well...

--DDL

hey guys, any ideas how to discharge end capacitor after power - off [smiley=huh.gif] ? I mean placing a discharging resistor across cap, or to use dual switch for power, AND shorting cap . would that work? . I blew my LD by forgetting to discharge that damn cap

???... The cap SHOULD discharge through the diode when you power off. I've never had a problem with cap discharge except when I accidentally unplugged & replugged the diode into it's socket WHILE the circuit was energized...???

Dave

xanatos said:

???... The cap SHOULD discharge through the diode when you power off. I've never had a problem with cap discharge except when I accidentally unplugged & replugged the diode into it's socket WHILE the circuit was energized...???

Dave

Click to expand...

yeah, but Im thinking of another way to discharge cap. I powered on/off circuit without LD, and cap held charge which killed LD after I connected it.