Lo-D Drivers

[Hiemal]

Bump.

 

[Hiemal]

Remaining four have been sold.

I can make more of these if required, just send me a PM if you need some.

 

[Alaskan]

I wonder how effective heat sinking would be from the front side, against the plastic front of the regulator device? Any idea? What is the max voltage I can input into it? The reason I ask is I have six of the old version which doesn't have the metallic backside for sinking to. I don't know how much current I can push the older type to without heat sinking, or whether I can sink from that side of the device and if I can, when heat sinked that way how much current the older version can take without heating up so much it steps the current down to protect itself? If you don't know, I will just have to try and see.

 

[The Lightning Stalker]

I wonder how effective heat sinking would be from the front side, against the plastic front of the regulator device? Any idea? What is the max voltage I can input into it?

It isn't anywhere near as good. I have
tried it before and stuff will smoke unless
there is something on the back to take some
heat there. With the board on the back, it
will be better, though, especially if you
sand down the plastic some to make it a
little thinner. It isn't the same as
actually heatsinking the back. Arctic
alumina makes a good insulator if you have
a beep buzzer on it while it dries to watch
for short circuits.

 

[Hiemal]

Obviously the closer the input voltage is to the output voltage the less heat is generated. I'd say I'd shoot for around 2 volts overhead whatever the forward voltage is of your diode you're using.

Because it's such a variable thing in regards to how much heat is generated, I can't say for sure. If the inputs and outputs are close enough, for as much current as they can push out they'll generate very little heat. As far as max current, though, it'll be whatever the driver can handle; in the case of the old ones 4.4 amps is about the max, with these new ones, it's about 3.3 amps. If they get too hot, they'll just lower the current/oscillate.

Basically, without a heatsink you'll have a duty cycle. You'll need to let them cool down before they'll be ready to go at their max current again, if the temp gets too high. With a heatsink, though, the on time will be greater. With the new PCB's, the pad on the back will GREATLY improve how well these heatsink and how fast the heat is pulled away from the driver, so they, overall, should perform better with heatsinking.


As lightning said, sanding the fronts of the old drivers and using some thermal paste should give you the best results.

 

[Alaskan]

Thank you for helping with those questions, I was thinking of running several diodes in series and because of that, needed to know the maximum voltage I can feed into the unit. Perhaps these aren't well suited for running several laser diodes in series due to the higher voltage required to do so?

Also, is there a different regulator on the newer version? Why the 3.3 amp rating for these, which is lower than the first ones you built?

Appreciate your time answering

 

[Hiemal]

Thank you for helping with those questions, I was thinking of running several diodes in series and because of that, needed to know the maximum voltage I can feed into the unit. Perhaps these aren't well suited for running several laser diodes in series due to the higher voltage required to do so?

Also, is there a different regulator on the newer version? Why the 3.3 amp rating for these, which is lower than the first ones you built?

Appreciate your time answering

Well, the datasheet for the regulator specifies a maximum input of 60 volts. However the current sense amp can only handle a max of 36 volts, so.

36 volts should be the maximum you ever put into one of these.

And it depends on what your supply voltage is going to be. If you can series up several laser diodes to get the forward voltage as close as possible to the input without going within 2 volts, that'll give you the best possible run time, least heat produced, and just overall, better performance.


As to why these are rated lower, you know, I actually don't have a specific answer as to why they are. When I tested the old style boards, they could handle 4.3 amps.

These don't go any higher for some reason. I don't know if I got a weird batch of regulators the last time, or what the deal was but the current numbers make more sense given what the datasheet says the regulator is capable of.

 

[The Lightning Stalker]

36 volts should be the maximum you ever put into one of these.

Don't forget about the input/output caps.

 

[Alaskan]

I better check that! Thanx

 

[rhd]

As to why these are rated lower, you know, I actually don't have a specific answer as to why they are. When I tested the old style boards, they could handle 4.3 amps.

These don't go any higher for some reason. I don't know if I got a weird batch of regulators the last time, or what the deal was but the current numbers make more sense given what the datasheet says the regulator is capable of.

It's probably the current sense monitor. You're making these adjustable across a fairly excessively large range. 300mA to 3A is 10-fold. Assuming you're using a ZXCT1009, your min and max vdrop across the sense resistor is, I think, 50mV and 500mV, respectively. That's also a 10-fold differential. Going above 3A may simply be too much drop for your current sense monitor to handle.

 

[Hiemal]

Don't forget about the input/output caps.

Ah, right. Completely flew over my head, haha

Then the board's are limited to 10 volts maximum input.

Two cells, or up to 10 volts in.


And RHD, that doesn't seem to be the case (I use a 0.015 ohm resistor, and the ZXCT1109). I haven't noticed any problems with stability, either so... :thinking:

The new boards don't vary much, they can all do the same current range without problems. The old boards were the same way too. I didn't change any parts or do anything different between the two (other than layout changes) hence my confusion...

 

[The Lightning Stalker]

Ah, right. Completely flew over my head, haha

Haha, yeah, I have first hand experience of
that particular thing flying over my head.
Until you hear that distinctive crackling
sound and see smoke and the burning smell,
tantamules have chased me out of the house
on several occasions because they put the
stripe on the "wrong" side