FS: Mohgasm Linear Drivers

jcranmer · Nov 13, 2011

benmwv said:
I saw where you posted "undefined" before and thought I just didn't get the joke :crackup:

You weren't the only one!

Mohrenberg · Nov 13, 2011

benmwv said:
I saw where you posted "undefined" before and thought I just didn't get the joke :crackup:

Did you manage to get those c6-mohgasms in before the 3 week break on the pcb order?

Did the amc's turn out too thick to stack three?

the boards with an AMC7135 on it is about 3.2mm thick, and the diode pins on the 635 diodes are 6.6mm according to their data sheet, so we'd only be able to stack 2 for a max of 700mA

people could still just glue 3 of these these little things to their heat sinks and then wire it up by hand, you'd have a 1A 635nm driver for ~$6 that runs on a single cell.

the amc7135 chips arrive tomorrow according to tracking. they were in chicago yesterday

benmwv · Nov 13, 2011

Yeah, they are plenty small enough.

I bet you could even drive a 445 with them.
5x for 1.75A. They have plenty of on-board heatsinking.
It would have to dissapate ~1W on each board.

Ill try and make a board with two on it.

rhd · Nov 14, 2011

benmwv said:
Yeah, they are plenty small enough.

I bet you could even drive a 445 with them.
5x for 1.75A. They have plenty of on-board heatsinking.
It would have to dissapate ~1W on each board.

Ill try and make a board with two on it.

AMC7135s really suck for 445s. I have three designs, and about 30 PCBs each, of AMC-based 445 drivers.

They're great if you want to drive your 445 on 5.1V of input supply (seriously, that's all you need). But they suck if you want to use 2x lithium ions. You're basically dissipating 1W per IC. They are so incredibly tiny that this becomes a deadly task.

I had a quad-AMC7135 board that was intended for driving 445s. I even added some aluminum on top of the ICs to aid in heatsinking. With a 2x cell supply, they basically hit thermal threshold in 5 seconds.

benmwv · Nov 14, 2011

rhd said:
AMC7135s really suck for 445s. I have three designs, and about 30 PCBs each, of AMC-based 445 drivers.

They're great if you want to drive your 445 on 5.1V of input supply (seriously, that's all you need). But they suck if you want to use 2x lithium ions. You're basically dissipating 1W per IC. They are so incredibly tiny that this becomes a deadly task.

I had a quad-AMC7135 board that was intended for driving 445s. I even added some aluminum on top of the ICs to aid in heatsinking. With a 2x cell supply, they basically hit thermal threshold in 5 seconds.

Did yours have the tab of the amc hooked up to a ground plane or were they just on the little oval that comes with it?

These have a large ground plane on the top and bottom with about 20 vias right at the tab so I was hoping it could spread the heat over enough area to get away with driving a 445nm diode. I guess the only way to know is to try it.

plasmaninjaa · Nov 14, 2011

Hey, is it possible for me to hook up a pot to the output of this driver? I dont know if I want mine running at 1.8a all the time. It would be nice to bring it down a bit unless I really want full power.
if its possible, what kind ohm rating would I want for it???
thanks

rhd · Nov 14, 2011

plasmaninjaa said:
Hey, is it possible for me to hook up a pot to the output of this driver? I dont know if I want mine running at 1.8a all the time. It would be nice to bring it down a bit unless I really want full power.
if its possible, what kind ohm rating would I want for it???
thanks

It doesn't work like that - you can't put a pot in series with the output of this driver.

But, what you COULD do, would be to buy Moh's 1.25A version.
- Grab a 10 ohm pot, and a 2 ohm resistor, and wire them in series
- Then take that little assembly, and wire it in parallel with the resistor(s) on Moh's driver

That will give you a range of 1.875 A all the way down to 1.35 A

Mohrenberg · Nov 14, 2011

I may have an adjustable version in the future. I just need to prototype the board to make sure everything works okay.

Mohrenberg · Nov 14, 2011

my boards were shipped saturday from oregon. so they will probably be here wed or thurs.

jimdt7 · Nov 14, 2011

Does it needs heatsnk at 1.8A ?

Mohrenberg · Nov 14, 2011

It would be a smart choice. I normally just arctic silver them to the pill of the host. I've also got some 1/8" flat aluminum that i cut squares off of and glue to the driver when needed.

benmwv · Nov 14, 2011

Mohrenberg said:
I may have an adjustable version in the future. I just need to prototype the board to make sure everything works okay.

I really hope that pot adjustable version works. I went over the math like five times.

They will likely be a bit more expensive... They have more and smaller components so the will be harder to make.

@rhd and moh

Got parts today for boost. I'll try and get it in the oven in an hour or two, I'll let you guys know.

Blord · Nov 14, 2011

Mohrenberg said:
It would be a smart choice. I normally just arctic silver them to the pill of the host. I've also got some 1/8" flat aluminum that i cut squares off of and glue to the driver when needed.

Which side should be heatsinked if you have a choice ? The resistor side or the ic side ?

Mohrenberg · Nov 16, 2011

If at all possible you should heat sink both.
When heat sinking one side, I always go for the IC. Simply because that is what everyone does so I just follow the crowd.
When assembled with reflow soldering, these things withstand 450 degrees Fahrenheit (232C), so they aren't too easily damaged.

The boards came in today. I'll be shipping off pending orders over the next day or two.

mark-in-dallas · Nov 16, 2011

Great! I'm looking forward to trying them.

JuniorSG123 · Nov 18, 2011

Moh,
driver available for order?

FS: Mohgasm Linear Drivers

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