Hi all,
I am working on small PCB board which will turn on an off power supply of 4 AA batteries on specific time of a day. I am going to use following components:
Real time clock - DS3231
Attiny85
Servo motor
- correct transistor and resistor (which I would like to ask you for help).
Aditional hardware:
Attiny programer
Servo motor will work to open/close water valve at specific time of a day. This servo will be powered by the 4 AA batteries. The RTC + ATTiny will be powered by the CR2032 battery. There will be used the DS3231 alarm to wake the attiny85 chip and then the chip will power up by transistor the servo motor and will manage the direction. I would need to ask for help to use correct resistor + transistor for the specified servo motor. Please could you help me to find the right one for this application?
Thank you in advance.
I am sorry, but I never used transistors and I am a bit lost in so many types of them. So any advice will be appreciated (same for the resistor value.
This subject comes up occasionally. Search this site for "switch servo power" for some info on the circuit and components.
Two points form the forum posts on this subject.
The power switching needs to be on the high side. The electronics in the servo do not like to have their ground switched.
You need to turn off the PWM signal to the servo or you risk damaging the servo electronics. Either change the output to an input (HiZ) or insure that the output is locked LOW.
Thanks guys for your advice and help. What about to use this MOSFET module. It will be probably easier for me to implement it for the beginning testing purpose.
By the way, if I would use same MOSFET which is used in the module above - IRF520 - what resistor should I use? I mean if I would use just the IRF520 transistor separately (not the module itselve). Is the 100 Ohm resistor ok as you mentioned above? Thanks.
The MOSFET on that module is N channel so not suitable for high side switching. Besides that, it is not a logic level MOSFET. That means that an Arduino output will not fully turn the MOSFET on.
Ok. So I would ask the same question as in the beginning of this thread 
but then I would probably get the same answer. Like I said. I am lost in all the transistors and MOSFETs. That is the reason why I tried to describe the thing I am trying to build and asked for advice of resistor type. I wanted to ask people which are years of knowledge far away from me as I would spend hours of searching and then I would ask same question here to be sure I selected something suitable. Anyway thanks for your time trying to direct me the right way.
I also red this article. If I understand correctly there is also used similar N chanel MOSFET - IRF640. So like I said I would appreciate your advice on right MOSFET type for described application. And thanks for your time spend on my stupid questions.
If I would have enough knowledge to find answer for my question in 10 minutes in some seller web site, be sure I would not open a thread here in this forum and would not bother you. But as you can see when I come with some solution which I found, you comment it as not a right solution. Anyway, thanks for your time.
I found some info on google as you can see above. But when I presented here then I got answer that it is not suitable. I see that discussion in this thread is now more about that it is better to use google then ask here more experienced people. I did not want to fight here with anybody. I am sorry if my question was too stupid to ask. I was just lost in all kinds of transistors. But it was already said. Sorry guys that it looks now that I was not able to search on google but I did before I asked here. I do not know what more to say here. I am sorry in case I make you unhappy or how to say, to see such question here on Arduino forum.
I found some info on google as you can see above. But when I presented here then I got answer that it is not suitable. I see that discussion in this thread is now more about that it is better to use google then ask here more experienced people. I did not want to fight here with anybody. I am sorry if my question was too stupid to ask. I was just lost in all kinds of transistors. But it was already said. Sorry guys that it looks now that I was not able to search on google but I did before I asked here. I do not know what more to say here. I am sorry in case I make you unhappy or how to say, to see such question here on Arduino forum.