Amplifying a TTL signal?

[things]

Just to give you a idea on my setup. I have a laser module, which s connected to its OWN driver. The laser driver has MODULATION input. I have another little circuit board, which is the one that SENDS the modulation signal. My problem is, the board that sends the signal isnt supplying a powerful enough signal to fully trigger the laser driver, so I am trying to amplify it abit. So I am not trying to power the laser from it, it is JUST the modulation.

EDIT: I cant get a diagram of the laser driver board, because I didnt make it and the diagram isnt on the web anywhere, but have a look at this post as to some idea how it is setup

 

[Torben]

Just to give you a idea on my setup. I have a laser module, which s connected to its OWN driver. The laser driver has MODULATION input. I have another little circuit board, which is the one that SENDS the modulation signal. My problem is, the board that sends the signal isnt supplying a powerful enough signal to fully trigger the laser driver, so I am trying to amplify it abit. So I am not trying to power the laser from it, it is JUST the modulation.

Yes, that's what the circuit snippet I posted is intended to work with. You are powering the laser independently and, as I understand it, need to supply a +5VDC signal to the trigger input to turn the laser on, and remove that signal to turn the laser off. Is that correct? I know the part about independently powering the laser is right

EDIT: I cant get a diagram of the laser driver board, because I didnt make it and the diagram isnt on the web anywhere, but have a look at this post as to some idea how it is setup

Can you see the numbers on the chips on it? It is sometimes helpful to draw a small schematic of the output section of a board like that so you know what you're dealing with, if that information isn't available elsewhere.

If you can post very clear photos of the top and bottom of the control board it might be possible to tell what kind of signal you should expect from it.


Torben

 

[things]

I think it would be abit too hard to draw the circuit, its a double sided board, and is quite complicated, since it also controls the laser scanners. Basically, is there any way you can have the transistor amplify the + side instead of -?

 

[Torben]

I think it would be abit too hard to draw the circuit, its a double sided board, and is quite complicated, since it also controls the laser scanners. Basically, is there any way you can have the transistor amplify the + side instead of -?

If you mean what I think you mean, you want high-side switching, which you can do with a PNP transistor like a 2N3906. Is there a datasheet or instruction manual for the control board?


Torben

 

[things]

There is the manual, but it doesnt seem to offer and diagrams. https://www.electro-tech-online.com/custompdfs/2008/08/20KPB.pdf

 

[things]

I just got this diagram here, does it look like it would work?

Would it work with TIP41C's? I just have a few laying around, nd if want other ones I have to scrape through all my other crap to find something lol

**broken link removed**



EDIT: im going down to jaycar tommorow, so dont worry about the TIP41C thing

 

[Torben]

I just got this diagram here, does it look like it would work?

Would it work with TIP41C's? I just have a few laying around, nd if want other ones I have to scrape through all my other crap to find something lol

**broken link removed**

Did you get that schematic from the people who made the board?

That's similar to what I posted earlier with different resistor values and doubled up to be non-inverting. I'm not sure R2 is necessary. It should work, but in the same way that what I posted earlier works (just inverted). Not being sure how you hooked everything up, it's hard to say for sure.

Without knowing what speed you need, it's hard to say whether the TIP41Cs will work for you. I would still suggest using 2N3904s.


Torben

 

[things]

Well the scanners can scan at about 30,000 points/s, so it needs to be pretty fast and accurate. The diagram was made up by the guy I bought the laser off, he doesnt make them but he has a pretty good idea how it works and what I needed .

 

[Torben]

Hi Things,

The more I think about this, the more I think Eric is right: it's not a simple TLL high means "laser on", etc. Or rather, it is on the laser module side, but the output from the control board is a modulated TLL pulse train. If this is the case then the problem may not be the wiring or drive current; it may be in the setup of the control board. It may be set to only drive that output at a low duty cycle, so the laser appears dim.

On of the reasons I am thinking this is that the manual you posted says that the board has "3 laser Mod output, TTL", which is what I assume you're using. I think "Mod" stands for "Modulated".

Of course at this point I'm just guessing but that seems reasonable to me. It also means that this is what I missed in Eric's earlier post: the low duty cycle would both register as a low voltage on your DMM and cause the laser to appear dim.

How is the modulation set on the control board?


Torben

 

[Torben]

Well the scanners can scan at about 30,000 points/s, so it needs to be pretty fast and accurate. The diagram was made up by the guy I bought the laser off, he doesnt make them but he has a pretty good idea how it works and what I needed .

Well, in your place, I'd try it. The TIP41Cs I think are fast enough for 30kHz and might work. But again, if they do work, they are real overkill and slower than 2N3904s.


Torben

 

[things]

The 3 output Mod is for if you have a Red Green and Blue laser module. I only have green, so I am only usiing 1 of the mod outputs. Yes the Mod is for modulation.

On the control board, there is no pot or anything, its basically a pre programmed control board. It has its own effects. THe modulation is set to be highest, otherwise it would be a analog laser. THe TTL signal worked fine on the smaller laser module I had n there before, but the bigger laser requires a higher TTL input by the looks of it. So simply, all I need to do is give the existing TTL signal a little boost, so the laser is it full brightness.

 

[3v0]

The 3 output Mod is for if you have a Red Green and Blue laser module. I only have green, so I am only using 1 of the mod outputs. Yes the Mod is for modulation.

On the control board, there is no pot or anything, its basically a pre programmed control board. It has its own effects. THe modulation is set to be highest, otherwise it would be a analog laser.

Why is less then highest modulation analog ?

THe TTL signal worked fine on the smaller laser module I had n there before, but the bigger laser requires a higher TTL input by the looks of it. So simply, all I need to do is give the existing TTL signal a little boost, so the laser is it full brightness.

That feels wrong to me. Which is why I asked if you were driving the laser with the signal in the first post.

It feels wrong because a logic level signal feeding a logic level input does not use much current. I would think if the laser needed more current it would get it with transistors onboard and not expect the user to provide it on the control line.

If the controller worked with a similar but lower output laser it should work with this laser too: if it is controlled in the same way. It could be that the controller in incompatible with the laser.

Are trying to modulate this laser faster then it can handle.

 

[things]

Nope, the laser can be modulated at MUCH higher speeds than I am trying to run it at. I think its jut a design flaw in the program board, because there is another guy on a different forum with the EXACT same problem as me.

 

[3v0]

Nope, the laser can be modulated at MUCH higher speeds than I am trying to run it at. I think its jut a design flaw in the program board, because there is another guy on a different forum with the EXACT same problem as me.

Time to drag out or get your hands on a scope.

It would help bunches if we had schematics / data sheets / specs for the laser and control board. Without we are all shooting in the dark.

 

[Torben]

Why is less then highest modulation analog ?

I have the same question.

That feels wrong to me. Which is why I asked if you were driving the laser with the signal in the first post.

It feels wrong because a logic level signal feeding a logic level input does not use much current. I would think if the laser needed more current it would get it with transistors onboard and not expect the user to provide it on the control line.

If the controller worked with a similar but lower output laser it should work with this laser too: if it is controlled in the same way. It could be that the controller in incompatible with the laser.

Are trying to modulate this laser faster then it can handle.

I agree--this is what I was trying to get at in an earlier post too. Either the TTL level is high or it's low--there shouldn't be any in-between levels which would cause the laser to only turn partway on.

Things, you mention that the laser can be modulated at higher speeds than what you're using. Does the duty cycle of the mod input correspond to the duty cycle of the laser? If it does, and what you say about it being able to handle a much higher modulation rate is true, then perhaps what is needed is either A) a higher duty cycle on the mod input, or B) just tie the mod input high when you want the laser on.

If the control board is not capable of supplying a high enough rate to the laser, then one trick I might be tempted to try would be to trigger a pulse stretcher from the control board's mod output to present an unmodulated +5V to the laser's trigger input.

I hope a more experienced member will correct me if that's gibberish. It makes sense to me.


Torben

 

[things]

OK, I just built the circuit, but using 2N2222A 's instead. It works, but it is still quite dim. Anyone know which resistor I should change,remove to get more power through?

 

[Torben]

OK, I just built the circuit, but using 2N2222A 's instead. It works, but it is still quite dim. Anyone know which resistor I should change,remove to get more power through?

Did you read our earlier posts? At the moment, it appears that the problem is not with the power to the trigger input, but with its frequency and duty cycle. You have indicated (but not actually said) that running a wire straight from the laser trigger input to +5V turns the laser full on. That's a frequency of 0. The control board mod out is not providing a steady +5V, but is providing a chain of pulses which are too fast to be read accurately by your meter. While each individual pulse is probably reaching +5V (or close to it) the meter will show it as lower depending on the duty cycle of the pulses. I suspect that the laser is being turned on and off by the pulse train from the control board too quickly to see, but with enough off time that the laser looks weak.

This is just a guess based on incomplete information, you understand.

Again, I think you could achieve your goal by using a pulse stretcher to slow down the pulses from the control board out so that you can get the control of the laser that you want. It wouldn't be perfect but it should give you what you want.


Torben

 

[things]

The laser is designed to run from these pulses. It was built for laser show duty.

I cant slow it down, since it is for scanning, slowing it down would practically take away the whole blanking!

Maybe I can see if I can find what each potentiometer on the driver board is for, one could possibly be a input gain. Not sure.

 

[Torben]

The laser is designed to run from these pulses. It was built for laser show duty.

Yes, you've said that.

I cant slow it down, since it is for scanning, slowing it down would practically take away the whole blanking!

You need to state how fast it is currently going and how fast you need it to go before anybody can figure out what to do with that information. We are all in the dark here about what you actually have.

Maybe I can see if I can find what each potentiometer on the driver board is for, one could possibly be a input gain. Not sure.

Knowing that would be good, yeah.


Torben

 

[things]

Ahh fixed it. I just threw a 10K pot over R5 and adjusted it untill it was at brightest, and still had blanking.

Thanks for the help