What does TTL Modulation mean?

[hakzaw1]

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

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

Thanks to all for the info(EF, Wayne,HIMN, Dr.e.et al)-- Am I correct in this? blanking a laser by simply turning the power off and on(repeatingly)= bad/harmful for the laser---using TTL blanking --not harmful-correct?............hak

 

[Morgan]

Just to throw another query into the mix...

From what I've learned recently about TTL, it can work up to 30mHz whereas CMOS can only work up to about 1mHz. If professional laser display units usually only work to 35/40kHz then why not use CMOS? Less power consumption, lower voltages and smaller, cheaper packages. Is this simply a traditional or cultural thing?

Thanks,

M

 

[photonaholic]

Thanks to all for the info(EF, Wayne,HIMN, Dr.e.et al)-- Am I correct in this? blanking a laser by simply turning the power off and on(repeatingly)= bad/harmful for the laser---using TTL blanking --not harmful-correct?............hak

Yes Len, toggling the power is harmful, with TTL blanking, you can switch that puppy off and on 20,000 times a second, try that any other way.

 

[hakzaw1]

@photon...'you can switch that PUPPY off and on 20,000 times a second, try that any other way. '

Just love it when you talk technical-wayne:crackup:----------third option (and also not harmful) is a 'chopperwheel' if that is what it is called. true?

 

[photonaholic]

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?

No the best way I would do this is use a 555 to clock a 7474 or 7476 flip flop, perfect square wave signal. (Let me know if you need a wiring schematic)

Just to throw another query into the mix...

From what I've learned recently about TTL, it can work up to 30mHz whereas CMOS can only work up to about 1mHz. If professional laser display units usually only work to 35/40kHz then why not use CMOS? Less power consumption, lower voltages and smaller, cheaper packages. Is this simply a traditional or cultural thing?

Thanks,

M

just use the 74C74 or 74C76 flip flop, it's a cmos chip that behaves like a TTL.

 

[photonaholic]

@photon...'you can switch that PUPPY off and on 20,000 times a second, try that any other way. '

Just love it when you talk technical-wayne:crackup:----------third option (and also not harmful) is a 'chopperwheel' if that is what it is called. true?

1. I'm a redneck geek.

2. chopper wheels work, but very hard to time the blanking to create lettering or pictures.

 

[HIMNL9]

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?

No, it's a function, or a driving type, not reversing polarity.

Most of the TTL drivers turns the laser off when you apply the voltage to the TTL input, and turn it on when you ground it, or left it not connected ..... but some drivers works in reverse, turning the beam ON when you APPLY the voltage, and turning it off when ground or no voltage are applied.

If your driver works in this way, you have to reverse the TTL signal (usually almost all the programs for lasershows have this function already included, anyway, otherwise a simple inverter gate, or a transistor and 3 resistors, solve the problem)

Now, maybe, to make artificial analogue modulation?

Do you mean with PWM ? ..... but this require additional circuitry, and for fast scanning lines is still not the better solution .....




@photonaholic: you don't need a flip-flop ..... just use 2 gates in serie from an HC106 (it contains 6 inverting gates with hysteresis) ..... and the advantage is that if you need more current, you can parallel 2 or 3, or also all the 5 remaining gates, without any problems

 

[DakotaDaNative]

ok so mine is not a reversed ttl its a normal one. and i need a square wave so i want to use a 555 and whats this talk about an inverter? i have access to 4049's and those are easy to use. what im confused about now is why i need to flip flop the polarity. if it just needs 5v to turn it off ill pulse a high into the ttl with a 555 switching an opto isolator thats switching 5v directly to the ttl with the "g" lead grounded and that would be in the range of speeds i need. correct? if i need to flip flop the polarity ill just use the 4049 to invert the 555 signals on each pulse. i built a circuit like this for hdd arms.

 

[HIMNL9]

No, basically you don't need an inverter if the output is already square.

The inverter / hysteresis gate was for "square" the signal in case you don't have an already square wave signal.

%%% in standard configuration is already square wave.

 

[DakotaDaNative]

ok thats what i thought im sure ill be back with more questions thanks again guys

-Dakota

 

[Cyparagon]

You don't need a signal unless you need to modulate it. If all you want is to turn it on, a lithium battery across the TTL terminals will work fine (observe polarization).

 

[hakzaw1]

1. I'm a redneck geek.

2. chopper wheels work, but very hard to time the blanking to create lettering or pictures.

Gotcha-- I meant just as a means of safely stopping/starting the beam momentarily not for pictures or lettering.--TY--hak

 

[Lemorlenny]

Hi, a question,
I have some simple red and green pointer and module laser, how can i implement TTL, or other modulation with this objects?, I need almost 300Hz for my laser musical project.

Many thanks.

Lenny

 

[HIMNL9]

The thread is a bit old, you noticed ?

Anyway, for your problem, it depend from the type of driver that your pointers and modules have ..... if they are standard sink or source drivers, made with an op-amp and a final transistor, it's always possible to add some components for give a TTL mod to them, but still depend from the schematic of the driver ..... do you have it, or know it ?

 

[Lemorlenny]

The thread is a bit old, you noticed ?

:yh: yes it is, but seemed the most appropriate in my googled search, sry.

Anyway, for your problem, it depend from the type of driver that your pointers and modules have ..... if they are standard sink or source drivers, made with an op-amp and a final transistor, it's always possible to add some components for give a TTL mod to them, but still depend from the schematic of the driver ..... do you have it, or know it ?

For example i boughten one of this, cheap 50mW but decently efficent:

I have not schematics at this moment but i can try to find it if helpful.

I have a little expertize in electronics but i ain't idea to how hack this module to insert TTL modulation from my pic or oscillator.

My goal is to try to found the cheapest way to make a popular Harpa Laser project.

Any suggest are welcome (also to buy a real ttl device ).

Thanks in advance.

(ps. excuse me for my poor english)

 

[Leodahsan]

I'm no expert on electronics,

but, can't a transistor be used for this purpose?

btw, the output transistor (I think) is the one under the big resistor (R1). He heats a lot