Jump to content

Stargazers Lounge Uses Cookies

Like most websites, SGL uses cookies in order to deliver a secure, personalised service, to provide social media functions and to analyse our traffic. Continued use of SGL indicates your acceptance of our cookie policy.

sgl_imaging_challenge_banner_through_the-_eyepiece.thumb.jpg.cb85f690376dcb3053c747827de6bf9e.jpg

BUDA

New Members
  • Content Count

    7
  • Joined

  • Last visited

Community Reputation

0 Neutral

About BUDA

  • Rank
    Vacuum

Profile Information

  • Location
    Hungary
  1. Hi Alan, Of course! I see the divider has no use there. Ehh... I do not know why I can not see these by myself? The new schematic does need the voltage divider only because the BC547 ransistor (what I have) does not withstand the 12V between its' base and emitter. I hope this will be the final version, I can't wait to try it out.
  2. Thank you very much for the info about the internal pull up! So it seems the internal logic is 3.3V based, and 5V tolerant? According to that I updated the schematic. I also ran a simulation how it should behave in theory. (At least the part with the internal pull-up of the mount) Finally it makes ~0,09V for LOW and ~3,3V for HIGH. If the simulation does calculate well. It should work I think... Maybe I should try to reduce the LED currents... but even if I have to buy a new 9V battery for every 2nd setup... so be it. Well to buy a rechargeable sounds even better. Edit: In the simulation I changed the voltage divider values ( multiplied by 10) but did not change the outcome significantly. As you see. The values I written belong to the 6.8k and 4.7k resistors.
  3. Thanks pete_l! Nice piece you picked! I just did not found it in a DIP package. Does such exist? I do not have the hands for soldering SOIC, and I also planned to simply draw the PCB by hand with permanent marker... But maybe it would worth to move in this professional direction... I'll think about that, thaks 1 more time!
  4. Hi Alan, I am not sure how do you mean that the TTL in/outs are swapped over... I assume it is just a "point of view" problem. R1OUT pin on the MAX232 IC gives TTL signal and goes to the mount direction. Therefore on the RJ45 connector side I marked as TTL_IN.... Well it is misleading indeed, but finally OUT from something, usualy also means IN to somewhere else. So depends on my "point of view" Now in the new schematic I finally managed to use the internal pull up in the MAX232. I did not measure yet, just assume the 400kOhm as shown in the Maxim specification usually (however I have a Texas Instruments manufactured one... does it make any difference?) To get that working, I had to invert the signal coming from the mount. The only drawback is, that this way an almost constant ~20mA current drawn from the battery through R1 by this signal line only. An old style battery last approx 4-5 hrs with 100mA consumption... hope so. I did not measure wether there is a pull up in the mount yet, but is it sure that it will be a pull up? (if there is any) while the MAX232 has pull down resistors on the RS232 in/out pins. Hm... I am a bit confused now. Anyway I attach my latest attempt. I kept the other direction intact until I find out if there is some pull up/down in the mount. I doubt that I will have time until the weekend to measure the mount, but at least I will not borther you for a while. (I keep my mount/scope in my parents house, they live in a close village. I live and work in the city with nice bright LED and all kinds of lights, and small flats... ) Peter
  5. Thanks Alan for the hints again! Nice idea to use the internal pull-ups indeed!! It would do the circuit less complicated again one bit. But as you also pointed the pins source/sink capability... I checked the datasheet and did not found such definition. So ... just to be sure, I made it more complicated again! (most likely I am the biggest enemy of myself ) Finally I added two transistor to switch the 15-20mA current of the diodes, and also I inverted the idle state of the optocouplers by getting their output grounded when not driven. Thanks again for the help, and I will post here how is it working/not working in real... Kind regards, Peter
  6. Hi Allan, Thanks for the checking! I found regarding Rx Tx connections, that they are ok finally, just my MAX232 IC is represented as mirrored in the schematic. It is so in the design software. Regarding over-complication... yes, it is. As you pointed out, there is really no need for the second 7805! Thanks!!! And now... the reason why I made this is exactly what you described at the end of your post. I plan sitting in the room on a cold winter night and control the mount outside. Most likely my laptop docking station wall adapter, or PC supply, and the one running outside will not be the same.... So I think I will update the schematic in the afternoon and give it a try... Do you think it might work finally?
  7. I am about to build an EQDIRECT adapter to connect my laptop and HEQ5. I have a notebook docking station with good old serial port (I tought) so I planned not to struggle with usb to serial port finding, porfilic or FTDI, etc... BUT(!) make my own cheapo EQDIRECT.... Unfortunately I am not an electrical genius, but I learnt somewhat. And as I read the schematic a bit closer, I had a bad feeling about connecting the ground of the notebook serial port and the mount ground potential. Then, I aimed this topic in searching, and I found some issues that might be in connection with that. Now I am a bit afraid to buildmy own, based on the given schematic on the EQMOD website. (no offense) So I tried to figure out how to avoid problems with grounding. Here is what I came up with. Maybe it is an ... how to say ... overkill, but I do not want to be the one in the million, who burt his mounts' electronics becuse of a ground loop. I hope that there is somebody around with more electrical skill, who can check it and tell if it is a complete non sense idea or...? Some explanation: As I read, connecting the grounds no problem in case of batteries, or between DC power supply and batteies but two not well chosen DC power supplies are able to make some serious smoking... So I implemented an intermediate battery powered stage, which is in connection with the notebook RS232 line only, and the mount is fully isolated from those by optocouplers. Ah sorry! I just saw when I uploaded the pic, that possibly the optocoupler output signals must be inverted. While for example logic 1 from the mount would give logic 0 on the MAX232 input. So the other pin of the optocoupler should be used for reading the proper values, and pull down resistor instead of pull up resistor... but the principle of a battry powered "insulation" is the same. Well, some batteries and the circuitry still much cheaper than a new mount/laptop... what do you think? I appreciate all your comments!
×

Important Information

By using this site, you agree to our Terms of Use.