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What does TTL Modulation mean?

iskor12

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I feel rather dumb to ask this, but I'd really like to know. Espicially if I buy a laser that has it/uses it?
 



ndrew2505

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it basically just cuts the laser on and off. analog fades in brightness.
 

dr-ebert

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TTL = Transistor-transistor-logic. It's used in a system of digital logic ICs that uses +5V for "hi", "1", "true" or "yes" and 0V for "lo", "0", "false" or "no".

TTL modulation means you can switch the device (laser) on & off by applying either 5V or 0V to an input pin (actually everything above 2.0V is "on", everything below 0.8V is "off", the range in between is "forbidden" and should only be applied for nanoseconds while going from one logic value to the other). This is opposed to "analog modulation" where the output intensity would be proportional to the voltage applied to the modulation pin.
 

ElektroFreak

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TTL modulation is based on TTL signals. A TTL signal is a series of square wave pulses created by cycling the voltage between either 0 (low) or 5V (high)

A laser with TTL modulation uses these signals as triggers to turn the laser on and off (more or less, but the actual workings are a little more complex than this).

By using this ability to rapidly pulse the laser and combining it with high speed mirrors (galvos) it is possible to create very clean images.

EDIT.. oops didn't realize everybody and their brother already answered..
 

chipdouglas

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i will give an example of elektrofreaks term "clean images". lets say you want to write the word "LASER" with your scanner. w/out ttl all the letteres would be connected and ugly, with ttl it would be clean with no connecting laser light, each letter would be individual.
 

DakotaDaNative

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i just bought a 150mw red with ttl leads coming off the board. so if i read it right i can apply any voltage from 2-5V and control the brightness or speed of the flashing? 5v being high and 2v being the lowest brightness and speed? i have pulsed my 50mW green and gotten some cool effects but with an external circuit i also noticed at the higher end of the pulses it got brighter or dimmer while maintaining a solid line (to fast for the spiro to break up into smaller lines). i want to use my red in an rgv build and instead of playing with the amperage can i just use the ttl to get a good color blend?

-Dakota
 

chipdouglas

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i believe ttl works as on or off only. 5v on 0v off. i don't think it can be used like a pulsed driver if that is what you are asking

michael
 

DakotaDaNative

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you believe it works like an on or off switch? or pulse 5v to it to pulse the laser on and off?
 

HIMNL9

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Basically, is for turn them on and off really quickly, thing that you can't do just switching them on and off with the power switch ..... like in the lasershows, where you need to turn it off for a segment of line, for separate 2 figures ..... TTL modulations, usually, can work without problems til 10 KHz or more (try to do the same turning on and off the power switch 10.000 times each second ..... ;))
 

DakotaDaNative

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yeah i get that but chipdouglas kind of confused me. thats exactly what i want to do turn it off for a segment of the line but how slow do you figure i could get it? from what i think i understand until chip popped in 2v is slow speeds and 5v the highest? and would that be a solid signal inputed or would if be more like a saw tooth?

EDIT: hey chip i was also asking if you could use it as a pulsed driver but not drive the diode directly like a DRIVER does but pulse it like the ttl is meant to be used just super fast to adjust the brightness if i can do this with 555 im sure i could with the ttl.
 
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HIMNL9

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Uhm, no, this can be used only for turn on and off, and the speed don't depend from the voltage ..... basically, anything under a certain voltage (usually 2V, in some cases 1,2V), turn it on (or off, in the reversed TTL, and anything over 2/2,2V turn it off (or on, in the reversed TTL) ..... there's a small hysteresis zone in the middle, for avoid "flickering", but not too much .....

The speed of the turn on/off cycle is usually at least 10 KHz, in most of the professional units can reach easily 35/40 KHz, and in telecommunication modules you can drive them at MHz range (but this speed have no sense in lasershows) ..... and, ofcourse, being TTL, more the signal is squared, better it is .....
 

DakotaDaNative

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ok thats where most of my confusion was. thanks for the info now i just gotta check the specs on mine and get started with some experimenting.

-Dakota
 

FireMyLaser

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Uhm, no, this can be used only for turn on and off, and the speed don't depend from the voltage ..... basically, anything under a certain voltage (usually 2V, in some cases 1,2V), turn it on (or off, in the reversed TTL, and anything over 2/2,2V turn it off (or on, in the reversed TTL) ..... there's a small hysteresis zone in the middle, for avoid "flickering", but not too much .....

The speed of the turn on/off cycle is usually at least 10 KHz, in most of the professional units can reach easily 35/40 KHz, and in telecommunication modules you can drive them at MHz range (but this speed have no sense in lasershows) ..... and, ofcourse, being TTL, more the signal is squared, better it is .....
Now, maybe, to make artificial analogue modulation?
 

DakotaDaNative

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wait what do you mean by reversed ttl? do you mean reversing polarity on the leads or is that a function varied by the model you buy?
 

photonaholic

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TTL modulation is on/off only. any attempt at otherwise will stress the circuits and burn things out.

When working with TTL, savvy builders will tie unused inputs to either +5 volts or ground to prevent unwanted "floating" of the voltage. Laser drivers are usually already "tied" with a resistor, so you can operate the laser as-is, but can easily force it to the off state.

 
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DakotaDaNative

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ok i see i take mine is already tied because i can operate it without any signal input to the ttl. so that means i just send in 555 pulsed high or low but since it probably tied to +5 should i use a diode and just pulse neg into it? and i have two leads do i tie one to a ground voltage or just leave it? i think ill probe around with my meter. sorry for all the stupid questions and i kinda stole this thread from iskor but im new to ttl so i figure people are gunna see my questions and learn like i am. oh and just looking at it im pretty sure that the lead labeled g is grounded and that makes sense the other lead is labeled c for control possibly?
 




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