FlexMod P3 Disaster

[lasermaster1977]

Being an old fart of the laser world and trying to rejuvenate my past passion for the art for solely non-commercial and personal pleasure, I researched and scoured the Internet and also sought guidance in the wealth of experience on this forum for recommended LD drivers in the less and one amp range. I had read a lot of posts on this forum and elsewhere of how good the FlexMod was. Having ordered and received three with the "optional" threshold beam suppression I was very impressed with the quality of work and design of the P3, and wow! how compact it is. And, I like to know as much as possible about how something works before I begin using it so I spent lots of time inspecting and researching what components were used. What I found out about what makes the P3 tick seemed to be very contrary to a few discussions I read about P3 but I don't really care about that.

No doubt I am now a member of the prestigious group who have burned up FlexMods. I believe, however, that this may have been averted if there were better descriptions in the sales and users manuals. I honestly don't know for sure though, so the purpose of this post is to share what happened to me so that others may avoid the same mistake(s). Also, I am no stranger to digital and analog electronics design, electronic components, computer and computer component designs, and software design.

I read where the FlexMod P3 could be purchased either in standard model, one that had interlock safety shut-down capability and one with the threshold beam suppression option. Dumb me, I thought the use of the suppression was an option, that although the suppression option came with two resistors and insulation tubing one could choose to use it or not. I understood that using the suppression option resulted in giving up the interlock capability.

Thumbs-up! The P3 User Manual clearly shows and describes how to place the two resistors for the suppression option.

I didn't see anywhere in the User's Manual where I HAD to first install the suppression resistors before setting up the threshold and gain so I proceeded with the "Setup and operation" steps EXACTLY as described (but leaving the suppression resistors off for the time being...does that make me a bad person?).

I had all three P3's MOSFETS mounted solidly on a 3/8" x 3" x 5" thick plate of 6061 aluminum heatsink along with a 7812 1Amp voltage regulator used to power the P3's. I was setting up the P3's, one at a time, for use with a very nice RGB Bundle consisting of a 120mW Red @ 165mA Gain and 50mA bias (HL63603TG), a 50mW Green @ 150mA Gain and 50mA bias and a 120mW Blue @ 120mW Gain and 30mA bias, all stated in electrical powers and currents.

Each P3's bias trim pot was adjusted to the required mA for the associated LD, until all three P3's had their bias' set correctly. I then started to adjust the first P3's Gain (with the Mod input @ 5v) but the drive's current reading on the meter did not change on my amp meter as I turned the pot clockwise. It was then that I found the heatsink to be very, very hot, "abby-normal" hot. I powered everything down wondering, WTF! and chastising myself for not monitoring the 12V regulators current output. I let everything cool down then setup for another P3. Same thing, and same for the third P3. I figured at the very least the MOSFETs were "open" or "shorted". They turned out to be "open" where you don't want them to be. I checked the .2 ohm resistors and they were still good.

I went back to this forum and searched for anything and everything P3 related and read it. That's were I saw other mentions of the P3's software code and it being uploaded only at time of manufacture, not something that can be done....and that the suppression option had "different firmware" than the standard version. Common guys...really? But these posts did affirm that the most common damage was to the MOSFET and possibly sometimes the dual Op-amp on the bottom of the board.

Scrutinizing the P3 circuit board and components again on all three boards, I did find something they all had in common and which indeed could be described as a firmware version of sorts. They all had scratches on the top-side of the PC board just under the large resistor that cut through several traces.

This made me wonder whether those resistors were required prior to setup, so I replaced the MOSFETs, soldered the resistors in and re-tested. This time nothing got hot, the red LED light came on but I could set the bias on two of the P3's, but not the third. The op-amp is a bigger pain to swap out so before I go there...any comments?

[absolom7691]

Because you didn't install the beam supression, did you remember to hook up "interlock" to V+?

[lasermaster1977]

Because you didn't install the beam supression, did you remember to hook up "interlock" to V+?

Thanks for your response. Yes, absolutely.

[lasermaster1977]

I believe I've made progress into understanding what probably happened that clobbered my first three P3's. It most certainly was not a P3 problem.

After identifying virtually all of the SMD components I decided to skip over the single and dual op-amps and focus on testing the diodes. Of the three diodes per board only three survived, 3 out of 9, two on the GRN P3 and one on the BLU P3.

So here is how the P3s were wired up and why it all went wrong for all three boards in one fell swoop. I had soldered 10 in., color coded wire pigtails of 18 gau., stranded wire to all connection points, GND, V+, M+, Out-, Out+ and a jumper between Interlock and V+.

Since my total expected current draw for the RGB diodes running max. current was 415mA, and adding another 100 mA worst-case of P3 operational overhead, I chose to use a uA7812 12v/1amp regulator in a TO-220 case that bolted to the same heatsink the P3's were on. I feed the 7812 with a 18v/1.11amp DC regulated wallwart.

The GNDs and V+ terminals of the P3's were daisy chained to the GND and 12V outputs of the 7812. The M+'s were tied together and jumpered to the 7812 GND terminal with quick-connects.

Each Out- was shorted to it's Out+. My Fluke 8060A (I know, it's an oldie)set in current mode was then connected in series to one Out- and Out+ and the BIAS was adjusted to the desired mA reading for that intended LD. All three P3's were set successfully and had their minimum RGB LD threshold BIAS settings set. It was all going very well. I powered off the wallwart.

I then took the three twisted M+ wires loose from GND and jumpered the 7812 GND to the GND of an external regulated, current limited, 0-20v/0-3A dual DC lab grade power supply. I jumpered the M+ wires to the V+ out of one of the regulated supplies that I had preset for a 5V output. I set the current limit to mid-range. This is the start to what exactly one does if one wants to screw up all three P3's up at one time.

I checked all my connections and then connected a quick-connect jumper from the regulated supply to the M+ wires. I plugged in the wallwart and turned on the my variable 5v source and tried to set the first LDs max current. Very little happened on the current meter. I hadn't noticed the the dual power supply (which I inherited from a close friend) was configured for plus and minus supply output and I had plugged into the -5V side.

So all P3's M+ were at -5V for a few minutes while I tried to figure out why I wasn't getting any current reading, then I noticed the side of the dual supply I was using had a current output reading of over 1Amp. I touched the heatsink plate and it was cooking hot. I powered off.

That's what I did to screw up three P3's. But hey, I didn't let any of the smoke out. 3 more P3's have been ordered and overall a very inexpensive lesson learned considering.

[lasermaster1977]

My sincerest apologies to those on this forum for my being such an utter dick and doubting Thomas. This old dog learned that a "new" technology trick indeed exists and is used in the FlexMod P3. I have some great communciations with Andrew lately. I never in my wildest imagination or dreams would have believed that a six-pin microcontroller with flash memory could exist. My replacement P3's arrived today and I'm excited to get on with my build.

Go ahead, hit me.

[mixedgas]

My sincerest apologies to those on this forum for my being such an utter dick and doubting Thomas. This old dog learned that a "new" technology trick indeed exists and is used in the FlexMod P3. I have some great communciations with Andrew lately. I never in my wildest imagination or dreams would have believed that a six-pin microcontroller with flash memory could exist. My replacement P3's arrived today and I'm excited to get on with my build.

Go ahead, hit me.

You were not being a d!(#, you just happen to be the first case of a setup error with the new version of the P3.
Stuff like that happens.

No one knew what to say, and we didn't have enough info to comment.

Go in Peace, and Live Long and Prosper?

Steve

[WolfMax]

You're not the first to have issues with P3's that weren't the P3's fault. I thought I had blown 2 P3's when I could not get any output on the LD connections and the error LEDs kept lighting up. Turned out to be a blown fuse in my meter that I didn't discover until after buying 2 more P3's. Still I have a couple of spares now!

[drm916]

You're not the first to have issues with P3's that weren't the P3's fault. I thought I had blown 2 P3's when I could not get any output on the LD connections and the error LEDs kept lighting up. Turned out to be a blown fuse in my meter that I didn't discover until after buying 2 more P3's. Still I have a couple of spares now!

Spares are a good idea.. if you can find them

[JasonB]

lasermaster1977, your posts have great detail and I enjoyed reading about your P3 adventure. Your sequence for 'starting up' your P3s was very logical. I'd like to share something I've learned about the P3s, I have both the beam suppression version and a few without it.

Even after carefully setting up my P3s with a regulated lab quality DC power supply using a 0-5VDC modulation reference from the wiper of a pot on a separate power supply (0VDC on supplies tied together) while monitoring the Laser Diode current I found that I still had to adjust the bias and gain pots a bit later on. What I found real interesting is that my red LD will go off without the beam suppression feature, while my blue LD required the feature. [And I also found it interesting that the beam suppression version is different due to firmware, and share your fascination that there is a PIC/embedded controller whatever on there.] Anyway, on the suppression driver, a RED LED on the P3 illuminates when the suppression kicks in (I think thats the case; the modulation voltage to the P3 goes to 0VDC, the LD ghosts for a couple hundred milliseconds, then the LED goes on and the Blue LD goes off).

What is the point of this post? The point is I spent lots of time tweaking the pots after installation. In fact, at one point I got so frustrated I stopped using my DMM and slowly tweaked the pots while the PJ ran a test pattern, and tweaked until I got the results I wanted. Then checked LD mA with a max 5VDC modulation reference to make sure I was not exceeding the LD's max current....

I agree, the two-page document from Andrew could have some more detail (such as I think that red diagnostic LED illuminates in more more cases than indicating an interlock such as beam suppression on a different model, should there be two datasheet versions?), but what a great product and fun adventure to get them running!

Looking forward to reading more of your posts! Let's see that PJ build....

-Jason

[Draco]

Thanks for the post, interesting read, on a side note the name "abby-normal" that was from a garbage pail kids card from the 1980's if memory serves