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  1. HellasTechn

    Capacitive touch panel detecting false touch

    I suggest you make sure that the problem is not caused by some error in the PCB design or PCB related in general.
  2. HellasTechn

    Need help, 12v water pump

    if your water pump is a DC one then yes you should use only the DC output.
  3. HellasTechn

    4011 IC

    What voltage and current do you wish to switch on and off ?
  4. HellasTechn

    Two relays in series with flyback diode.

    Come to think about it the missing part is that the PCx + and - tags from the 2 relays are then fed to 3rd relay. The 3rd relay acts just like the manal switch feeding PC1 and PC2 one at a time to PC3 so the output of the manual switch and the output of the relay are in parallel and that might...
  5. HellasTechn

    Two relays in series with flyback diode.

    I am sorry for confusing you. I dont have the rest of the diagram now. I got a little confused by your diagram. But now it makes sense. When i get the rest of the diagram ill breadboad it and see :)
  6. HellasTechn

    Two relays in series with flyback diode.

    Not quite like that. I use half duplex configuration. Yes, though in my case because the data bus is RS422. I need 2 wires per PC. Your diagram is correct only i need double the contacts you show. I made a drawing of my diagram below. As for reliabilit i think i am good enough because in case...
  7. HellasTechn

    Hello, Welcome! (Introduce yourself)

    Welcome on board ! We are all here to share knowledge and experience.
  8. HellasTechn

    Two relays in series with flyback diode.

    Well critical for me it is :) I am building a system where 2 computers (PC1 and PC2) will talk over a single rs422 bus through the relays to an other computer (PC3). The mcu taps on the rs422 output of PC1 and PC2 and based on a code i wrote determines which PC (PC1 or PC2) should be connected...
  9. HellasTechn

    Two relays in series with flyback diode.

    All The above are correct. I will use the fuse anyway just in case it will go open faster (though very unlike) than the relays coil thus saving the relay. I do use an MCU to control the mosfet and i use a voltage sense resistor network. When the relays are disengaged i read the 12Volts stepped...
  10. HellasTechn

    Two relays in series with flyback diode.

    I am pretty sure i have read somewhere on the internet on a specific datasheet that a fuse (not a PTC one) with different voltage rating had different tolerance concerning its current rating. To be honest i have witnessed countless times the fast blow glass fuse on my bench psu withstanding 3-4...
  11. HellasTechn

    Two relays in series with flyback diode.

    One other thing that comes in mind is adding a serries fuse. The relay coils according to the datasheet are 90 Ohms each. (SCHRACK RT424006). the current they consume under normal circumstances are about 66mA. Considering Ohms law, two relays in serries under 12V should still consume 66mA. If...
  12. HellasTechn

    Two relays in series with flyback diode.

    True. I am looking into it as we speak. P.S. Well the cost is prohibiting for me..
  13. HellasTechn

    Help understanding SMD PPTC fuse specs.

    Okay so Trip current if exceeded the "fuse" will introduce high resistance and will not allow more current to pass. Okay then the circuit must force current more than 100ma to "enable" the "fuse" to conduct but not more than 250ma. I think ive got it now :) P.S. like this one is wrongly labled...
  14. HellasTechn

    Two relays in series with flyback diode.

    Thats right davenn. I need to switch 4 sets of poles (4PDT) but it is critical for my circuit that theese contacts are at the same state even under fault conditions. So running them in serries, i make sure that if one of the relay ciols fail of if the driving transistor fails then all contacts...
  15. HellasTechn

    Help understanding SMD PPTC fuse specs.

    I must be missing something. if the above is correct then how will that specific pptc fuse be able to protect a circuit that can not run above 100ma ? That specific fuse was titled as 100ma pptc fuse. maybe it was mistitled ?
  16. HellasTechn

    Help understanding SMD PPTC fuse specs.

    Thank you ! So this in fact could be compared with a 250ma fuse. Well in a way... So it can not be used to protect devices that max allowed current is 100ma.
  17. HellasTechn

    Two relays in series with flyback diode.

    each relay its own diode, like this ?
  18. HellasTechn

    Two relays in series with flyback diode.

    My question has to do wth the flyback diode in the below described circuit. I have two relays in serries (6V coil each) that are connected to a 12V source and controlled via a logic gate mosfet. I know that a flyback diode has to be placed as close th the relay's coil as close as possible but...
  19. HellasTechn

    Help understanding SMD PPTC fuse specs.

    So in other words the above fuse will restrain current to 100ma only after the load will draw above 250ma ? hold current is required to keep the "fuse" conducting ? mening that it will block below 100ma currents ? I dont understand...
  20. HellasTechn

    Help understanding SMD PPTC fuse specs.

    Hello everyone. I have this question now that i need help with. I have a GPS with an rs422 output. I want to protect its output from burning if short circuited to ground. According to the RS422 standard the RS422 lines have a max 150ma short circuit current. I want to use fuses in serire with...
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