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  1. HellasTechn

    how much current from RS422 output.

    Hmm that looks helpful. I thought it would be around 50ma. TI pdf's also state 150ma max driver short circuit to gnd current. What about rs232. Havent found anything yet.
  2. HellasTechn

    how much current from RS422 output.

    Hello everyone and Merry christmas. I have this strange question. In the past i accidently shorted the rs422 output of a driver chip and it got damaged. can i avoid it by placing a fuse in serries ? how much current can a typical rs422 driver deliver before it gets damaged ? I try to figure...
  3. HellasTechn

    DPDT relay lifespan.

    I understand. Thank you.
  4. HellasTechn

    DPDT relay lifespan.

    I think i understand what you say. In my case though i am not concerned about the relay contacts. I am looking for the relay's coil lifespan. In other words what im looking for is how many hours can it continusly be energized under 12V (with or without load on the relay's contacts) before it...
  5. HellasTechn

    DPDT relay lifespan.

    Good day everyone. I have a question concerning some relays i use for a project. I have been searching the datasheet to find the average lifespan in hours of the relays coil under DC voltage. The relay i use is the SCHRACK RT424012 and the voltage applied on its coil is 12V. Here is a link to...
  6. HellasTechn

    7805 regulator capacitors

    Thank you all four your advices. Special thanks to sir hevans1944 for post #23 Though i have seen many circuits using 7805 with aluminum electrolytic capacitor between the output and gnd, i guess that the people who wrote the datasheets know better thatn i do so i used the capacitors...
  7. HellasTechn

    7805 regulator capacitors

    Ive been thininking about the math... They didnt "add up" because i forgot that i took the current measurement at the input of the device, not at the 7805 output. So i was way off. I have measured the current going out the 7805 (actually consumed by the 5V circuits) and goes between 70 and 90ma...
  8. HellasTechn

    7805 regulator capacitors

    I know. I really do not know what to say. It probably has something to do with the 7805.
  9. HellasTechn

    7805 regulator capacitors

    Here are the actual readings. The actual resistor value is 26 Ohms and With 12V input under normal operation the circuit consumes 180ma, the voltge across the resistor is 2.4V and the input to the 7805 is 9.6V The measurements where taken without the diode so subtracting 0.5V (actual diodes...
  10. HellasTechn

    7805 regulator capacitors

    Okay that makes sense. In my case the 12V comes from an SMPS far from the regulators location. There are at least 5 meters of cable between. So i have chosen wrong capacitor values. I should go with what the datasheet recommends. I have to say though that i have seen 7805 regulators...
  11. HellasTechn

    7805 regulator capacitors

    do you mean i will reach the critical values for regulation ? For now i can say for sure that the system is working. Like i said i will check again with the dmm.
  12. HellasTechn

    7805 regulator capacitors

    Exactly. Yes but in my case 9V is not an option. I use 12V as input in my project which is used for driving orhter circuits and then it is stepped down to 5V to drive the microcontroller. I am going to double check with my multimeter and get back to you on that. 300ma is peak current...
  13. HellasTechn

    Auto Shut Down denon 1713 AVR

    It can be caused by so many different things. I think it is hard to say without taking a look at the actual unit. If i where you i would start with checking and replacing all the electrolytic capacitors. But thats only a whild guess.
  14. HellasTechn

    7805 regulator capacitors

    Thanks. I already know of them. My question is: how should i choose the input and output capacitor values ? I do need it to be as reliable as possible ant to last as long as possible. Also would it be a better idea to replace the aluminium capacitors with tantalum or with solid aluminium ?
  15. HellasTechn

    7805 regulator capacitors

    The 7805 comes in TO-220 package while the 78L05 comes in TO-92 package. They do the same thing but have different current and heat dissipation capabilities. Like i mentioned in post 1 i use the TO-220 version. R1 is there in order to drop the 12V down to about 10V thus reducing the thermal...
  16. HellasTechn

    7805 regulator capacitors

    Thats right. the TO-92 package can deliver up to 100ma. The TO-220 package can deliver up to 1A if mounted on a large enough heatsink.
  17. HellasTechn

    7805 regulator capacitors

    Why would i use a negative Vreg over Positive one ? I Dont think its a good idea to put the supply line on the tab of the 7805 (to-220) together with the heatsink. I risk touching the ground plane. Any thoughts about tantalum caps ? Searching the web i came across the Solid aluminium...
  18. HellasTechn

    7805 regulator capacitors

    I have an 7805 regulator feeding a microcontroller for some very important project of mine. I have seen many different schematics of 7805 regulator circuits and i see that they use different capacitor values on the input and output pins of the 7805. My question is: how should i choose the input...
  19. HellasTechn

    Battery capacity change

    You have to provide the full specs of the system before we can say for sure. I think you may be okay but charge time will be longer. Again i cant say for sure.
  20. HellasTechn

    Capacitor Substitution

    That Cap has definetly kicked the bucket ! Oops just realised you had already replaced it. So true !
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