pulse to a j15 3-pin connector.

[neutr]

Dear All,

I am not sure whether this is the appropriate section for my question, if not my apologies.

I want to control a Laser using a TTL pulse. I already made the program with labview by generating a pulse where I can control the high (should be +5Vdc) and the width. The program is fine as I can see the trigger(s) in the oscilloscope but I don't succeed in scanning the laser. The idea is to use the easiest way of scanning the laser named "Fast triggering of burst modes" but I am having some problems. I wonder if there is someone with experience on this issue. In the following I copy everything listed in the manual:

Fast triggering of burst modes:

To trigger a Burst step directly without using the RS232 interface, use the 3-pin Direct TTL connector, located on the Sunlite EX power module near its ON/OFF switch. Pin2 of the Direct TTL connector triggers a step only in Fast Burst and External Burst scans. Pin 3 goes high during all scans, GOTO and Burst motions. Definitions:

Pin      Name               meaning:

1         Ground            TTL signal ground Triggers a Fast Burst or External Burst step:

                                 - It will trigger on the rising edge of a pulse (0->+5Vdc)

2         TTL trigger       - In fast burst mode, the trigger duration must be 5ms < pulse < Delay time + Step time

                                 - In External Burst mode, the duration must be 50 ms < pulsewidth < Delay time

                                 - If pin 2 is held high, it triggers a series of steps

                                 - Pin 3 must be low in Fast Burst before pin 2 can trigger

3          Step Status    - Normally low; high (5 Vdc) during all motions; may be used to control other events.

I just want to use the Fast Burst mode. The idea is to set all the parameter in the laser (start, end, step, ....) and, if I understand correctly, whenever a TTL pulse reaches pin 2 the grating of the laser should move. On the other hand, at first, I made a BNC to the 3-pin connector by using only the pin # 1 and # 2. I thought that I only need to ground it and send the command, that the pin #3 is only from letting the user know when the motors are moving. I guess that is why I can not send pulses this way isn't it? The question is whether we can leave Pin #3 free or there is no other option but to attach it to another BNC cable and maintain it low. It also, when the TTL pulse is sent from Pin #2 do I also need to raise the Pin #3 signal to +5Vdc?

Currently I am making a second BNC cable to connect the ground with the first one's and the main connection to pin #3 but still I am not sure whether I can just keep low pin #3 and whenever I need the laser to move send a TTL +5Vdc pulse through pin #2.

Unfortunately, when I asked the technician his answer was "Page # 55 & 51 in the manual speak of TTL. I have never used this option." pages which I already checked (copied about). When letting him know that we need to use that option and if I can get in touch with someone else who worked with this issue, his second reply was "I have heard that the RS232 hook up in the back of the comp. is the easiest way to do this". but as I told him before his reply we need to use the other option! Furthermore, the manual clearly states that the option I am trying to use should be the easiest! but I am experienced enough to understand that his two replies mean "no, I don't know and there is no one to help you". Thus, I decided to post here for some help.  Can someone please give me any tip?

Thanks.

Best Regards,

[johnsold]

1. Tell the sales person from whom you bought the instrument about the poor service/lack of interest in helping you solve your problem that you received from the technician. Sometimes the service people are under pressure to fix broken things and get on to the next customer. They may not have any real incentive to help a customoer when it requires them to (a) think, and (b) do something which will take quite a bit of time and for which they do not get any credit.  The sales person, on the other hand, has the incentive of a satisfied customer who may buy other items or recommend the products to colleagues.

2. Do NOT connect line 3 low! Line 3 is a status output from the instrument. It is there to tell you whether the instrurment is ready to be triggered. You should monitor the state of line 3 and only generate the trigger on line 2 when line 3 is low.

Other things to check or consider: Are you sure the instrument is set up or enabled to accept triggers on the 3-pin connector? Does your pulse meet the timing requirements? Have you checked the status of line 3 with the oscilloscope while triggereing to make sure it is low? Does the instrument do anything when the trigger pulse is generated? Blinking lights, error messages, ...?

Lynn

[neutr]

Hi Lynn,

I am sorry for the delay in the answer but we had a problem with some equipment. Unfortunately even if I insisted I got no answer from the company regarding to the Fast External Triggering mode (they just skipped my questions). In any case, meanwhile I used the RS232 port and I am able to control the laser. I still want to make it work with the Fast triggering mode as I want the COM port for another use. I did not try to check the status of Pin #3 earlier as I needed another 8m BNC cable for that (I was just using Ground and Pin #2 to send TTL pulses). Now I already got another BNC cable and I will try to send a TTL pulse from Pin #2 and monitorize Pin #3 status. On the other hand, unfortunately there is no light indicating any movement. I can just check whether the grating moves or not.

I will keep you updated.

Thank you very much Lynn 🙂