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Cannot get TTL modulation to work on flexmod

DLProcessor

DLProcessor

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Having a bit of trouble getting TTL modulation from the flexmod n2. I applied 5 volts from a regulated ps to the driver and adjusted the bias and gain currents. Using my function generator I set a 0-5v square wave signal and applied it to the mod+ and mod- terminals. I hooked up the output terminals to an oscilloscope and observed that there was no square wave modulation at the output (i used a single regular diode as a test load). The output is just a regular DC signal.

I tried searching for an answer but came up with nothing. Maybe you guys can help.
 





chipdouglas

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i can not directly help but i could recommend you pm or email Dr.Lava

michael
 
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ElektroFreak

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DLProcessor said:
Having a bit of trouble getting TTL modulation from the flexmod n2. I applied 5 volts from a regulated ps to the driver and adjusted the bias and gain currents. Using my function generator I set a 0-5v square wave signal and applied it to the mod+ and mod- terminals. I hooked up the output terminals to an oscilloscope and observed that there was no square wave modulation at the output (i used a single regular diode as a test load). The output is just a regular DC signal.

I tried searching for an answer but came up with nothing. Maybe you guys can help.
Click to expand...

As I recall, if the driver is not under load, you get plain old DC output matching the input. If I were you I'd try hooking the driver to a load (test load or LD) and then see what you get..
 
DLProcessor

DLProcessor

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chipdouglas said:
i can not directly help but i could recommend you pm or email Dr.Lava

michael
Click to expand...

I sent this driver to Dr lava because I thought it was broken. I sent him pm's and emails to send it back for several weeks before he finally did. I dont think I can get a response from him quickly.

ElektroFreak, if you reread my post I mentioned that I used a single regular diode as a test load.
 
Hemlock_Mike

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How much voltage are you reading across this "regular" diode? If it's bad or reversed, it isn't providing any load. OOPS -- I guess that's what DrLava just asked...
An old LD gone LED makes a good load.
HMike
 
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DLProcessor

DLProcessor

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I hooked the diode anode to +OUT and cathode to -OUT. That should be forward biased, correct? Im sorry I cannot recall the voltage. Im away from my lab so I cannot check it right now.
 
DLProcessor

DLProcessor

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Ok I checked the diode voltage and it was 0.8v. However, this is a 0.6v drop diode I am using. Any suggestions?
 
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Solonar

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Add more diodes to total the voltage drop you expect for your final laser diode.

i.e. 6 diodes for a blu-ray, 5 for a 445, 4 for a red, or 3 for a IR.
 
DLProcessor

DLProcessor

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Ok I used 4 regular diodes as my test load but the driver still won't put out a TTL signal. I get 3.2v at the output but my oscilloscope is not showing a TTL signal. I don't know what I am doing wrong.

It would be nice If someone can make a tutorial on setting TTL modulation on lasers. I've yet to see one anywhere.
 
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Solonar

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Did you try just applying the signal to Mod+?

I assume you already did the jumper and set the currents as described in the manual.
 
DLProcessor

DLProcessor

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Yes, mod+ and mod- are connected to the signal generator and ground respectively and I have a nice blob of solder across the the "high" and mod+ jumpers.
 
drlava

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Is there a 0-5V square wave on the input? Some TTL outputs expect a pull-up resistor, which if needed you will have to put in the circuit yourself. A 1k resistor to V+ to Mod+ will be fine.
 
DLProcessor

DLProcessor

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Yes its a 0-5v square wave. Do I put the 1k resistors to mod+ and V+? So I will need two 1k resistors?
 
DLProcessor

DLProcessor

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Bump, I really need help with this. I believe i am doing everything right but I cannot get it to work. If someone can make some type of video tutorial i would be very grateful. I am a good visual learner.
 
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