Welcome to Laser Pointer Forums - discuss green laser pointers, blue laser pointers, and all types of lasers

LPF Donation via Stripe | LPF Donation - Other Methods

Links below open in new window

ArcticMyst Security by Avery

Driver conundrum

sdistin

sdistin

0
Joined
Oct 22, 2011
Messages
19
Points
0
I'm putting together a 405 SO6J with 2 16340 Li Ions supplying the power and a blitzbuck v3.1 regulating the current to 445mA, but there's a problem. I put everything in my host except for the diode, leaving the leads hanging out the front so I could set the current. When I clicked the switch I got no voltage at my test load and I heard a high pitch tone from the driver and only 0.05V at the leads.
I thought perhaps there was a problem with continuity somewhere - tested that, no problems. So maybe my batteries suck. Together they provide 8.2V and can power my 1.25mA 445 M140 with no problem. Just to be thorough, I hooked up a 12V PS to the driver and it works as expected, pushing 444mA with no noise. Concerned that the driver/batts couldn't overcome the Vf of my test load I shorted some diodes so the Vf was only ~3.2...still no luck.

I'm at my wits' end; anyone have any ideas?
 





Wolfman29

Wolfman29

0
Joined
Jan 14, 2011
Messages
3,816
Points
63
It's probably the batteries. If you can drive your test load just fine with 12V, and your test load requires under 7V, then anything 8V+ should work on it. Have you tested it with another set of batteries?
 
sdistin

sdistin

0
Joined
Oct 22, 2011
Messages
19
Points
0
Nope, I wouldn't dare after what I've read here. I'm using Spider fire from DX, which may not be top-of-the-line but they power my higher current M140 just fine, so I'm betting they are adequate.
Am I right in assuming the high pitch tone is from the MOSFET?
 
Wolfman29

Wolfman29

0
Joined
Jan 14, 2011
Messages
3,816
Points
63
The high pitched tone is the inductor. Have you tried measuring your batteries' voltages while powering the device?

And what kind of driver does your 445nm use?
 
sdistin

sdistin

0
Joined
Oct 22, 2011
Messages
19
Points
0
I haven't measured the voltage while powering the soon-to-be laser, but I just calculated the Ri of the spiderfire batteries and the AW batteries I've used in my 445. They were 227mOhm and 127mOhm, respectively. I can't find the driver but its from ricktrent and is similar to this one
BTW, thanks for your quick responses.
 
Wolfman29

Wolfman29

0
Joined
Jan 14, 2011
Messages
3,816
Points
63
That inductor may operate at a lower frequency than the one used on the BlitzBuck, so it wouldn't necessarily produce a whine. Make sure you calculate the voltage. If the voltage sags to around 3.5-3.7V while operating it (or lower), it may not be able to output the voltage necessary for the high Vf of a 405nm diode. A 445nm diode, on the other hand, has a lower Vf, so even if the batteries sag, they may still have enough voltage to feed to the driver.
 
sdistin

sdistin

0
Joined
Oct 22, 2011
Messages
19
Points
0
The batteries drop to 7.88V together which could potentially make it difficult to power a Vf over 6.63, (Vin*.85, from the data sheet) but even when I lower my test load to a Vf more like a red LD I still get no voltage across my 1 Ohm resistor. I wish I had a bench power supply.
 
Wolfman29

Wolfman29

0
Joined
Jan 14, 2011
Messages
3,816
Points
63
Oh, right, forgot about that bit. And you're sure everything is fine continuity wise?
 
sdistin

sdistin

0
Joined
Oct 22, 2011
Messages
19
Points
0
Yep, I've tried it in and out of the host to no avail. I think I'll have to buy a new one. Out of curiosity: is there any significance to the fact that it only whines when hooked up to the batteries but not the 12v PS?
 
Wolfman29

Wolfman29

0
Joined
Jan 14, 2011
Messages
3,816
Points
63
That's what makes me think it's either the battery or the test load. They typically whine when they aren't getting enough current. What was the current rating on the 12v PS? It works perfectly when hooked up to 12V, so it's not the driver.
 
Last edited:
sdistin

sdistin

0
Joined
Oct 22, 2011
Messages
19
Points
0
It held steady at 444mA. Perhaps a poor connection from the host to the driver would be enough for my DMM to buzz continuity but not enough for significant current. And since my 12V supply was clamped on to both the V- ring and the contact on the other side, it may have circumvented that problem. I'll test that hypothesis in the morning, though it seems a long shot.
 
benmwv

benmwv

0
Joined
Sep 10, 2010
Messages
1,380
Points
48
One thing I will mention is that many people just find some spot on a contact board that is connected to the plus and minus. For all we know you could be connected to a pad which is getting its connection to the battery plus through a 8mil trace going all the way around the board. This probably wouldn't drop so much voltage but worth a shot.

Solution, drill a hole in the middle of the board and soldered your wire directly to the bottom side contact.

Also I believe most meters will beep up to at least 10 ohms, maybe more.
 
Wolfman29

Wolfman29

0
Joined
Jan 14, 2011
Messages
3,816
Points
63
There aren't any of those spots on this board :\ Anything that connects to plus and minus goes through the board all the way to the exposed pads beneath.
 
benmwv

benmwv

0
Joined
Sep 10, 2010
Messages
1,380
Points
48
Oh didn't realize he was using a blitzbuck with contact board built in! I meant when people use random led driver boards for a contact board.
 
You must log in or register to reply here.




Top