How to tell analogue from ttl modulation?

[jaycey]

Ive got a green module with a seperate psu/driver, is there and easy way to tell if it supports ttl or analogue modulation?

Theres a red & black wire coming from the psu/driver that is not connected to anything so I assume this is for the modulation connections.

Heres a picture.

[ElektroFreak]

I have a laser with that exact same PSU and it's TTL.. but about the only way I know of to see for sure is to attach the modulation lines to an adjustable power supply and gradually apply voltage up to 5V. If the laser gradually increases in brightness as you apply voltage it is analog, if it suddenly pops on full-strength somewhere between 0 and 5V, it's TTL.

[norty303]

Also, if you power up the psu without anything connected to the modulation lines and the head lases then there's a pretty good chance it is TTL as quite a few TTL lasers work on a TTL- signal being present to switch them off rather than on. Apparently this is to stop lasers being sent back as 'broken mate' because the buyer didn't realise it needed modulation signal first.

[mixedgas]

I have a laser with that exact same PSU and it's TTL.. but about the only way I know of to see for sure is to attach the modulation lines to an adjustable power supply and gradually apply voltage up to 5V. If the laser gradually increases in brightness as you apply voltage it is analog, if it suddenly pops on full-strength somewhere between 0 and 5V, it's TTL.

One other way, short the two leads together, low cost TTL drivers use the fact that older logic gates could both source/sink current. So if you short the inputs and the laser lights, its TTL.

AAA or AA cells work just fine for this test, you get 1.5V, 3.0V and 4.5 v for 1, 2, and 3 cells.

TTL should threshold on at 1.8-2.4 volts, if adding the third battery gets you much brighter, good odds its 0-5V and analog. You can do this with a potentiometer and some sort of power supply, but do not exceed 7V to the laser.

Steve

[jaycey]

Well its lasing fine without anything conected to the modulation leads so thats the first step.

I'll give the AA cells a go.

Cheers fellas.

[LaserLover]

One other way, short the two leads together, low cost TTL drivers use the fact that older logic gates could both source/sink current. So if you short the inputs and the laser lights, its TTL.

AAA or AA cells work just fine for this test, you get 1.5V, 3.0V and 4.5 v for 1, 2, and 3 cells.

TTL should threshold on at 1.8-2.4 volts, if adding the third battery gets you much brighter, good odds its 0-5V and analog. You can do this with a potentiometer and some sort of power supply, but do not exceed 7V to the laser.

Steve

Just for safety sake and the survival of your laser, You might want to limit the current going from your batteries to the laser modulation port to avoid damaging the input side of the laser modulator driver (it might be poorly designed). Just add a 100 ohm resistor in series with the positive battery terminal. If you only have a 5 vdc supply use a 1 K potentiometer as a variable voltage divider but don't forget to add the 100 resistor to limit current to your laser modulation driver.

[The_Doctor]

What Steve said, though I suspect you can simplify it to any low-volt battery, as the input will then be off, full on, or somewhere between. If it's somewhere between it's analog. If there are exceptions to that you have a very sloppy mod circuit in the laser. Also what LaserLover said about that current limit resistor.

So basically a single cell and a series resistor. It won't tell you all but it will tell you plenty very fast, and safely.