First of all, I present myself. I am an industrial engineer, 27 years old. In my free time, I´m working in a personal project. Basically it is a kind of PLC than controls 150+ solenoid valves. The PLC is a modiefied Arduino platform with many UNL 2803 ICs (each Arduino output is 40mA max and it not enough). Each UNL 2803 can handle 500/600mA (50V max). The solenoid valves are 12VDC and 500mA. I´m using two UNL 2803 in parallel (one above the other) that handles 1000/1200 mA and have some security margin.
The idea is that the solenoid valves must open and close VERY fast and at a rate of 10Hz max (approx.). Each valve is controlled individually and the actual valves I bought have a response time of approx. 10 ms to open/close. This is perfect to me and works fine. The problem is that as solenoid loads are very inductive so I must add a Snubber / Transient voltage suppression to eliminate the peak voltage produced when the solenoid is turned off. If I don’t use some kind of protection, surely I will fry the ICs of the circuit!
Actually I´m using one 1N4004 diode parallel-connected to each solenoid. This protection works fine but it has a big controversial issue: the close time is widely increased (by 2x or 3x) and makes my system not to work correctly.
I´ve been searching for some alternatives that don’t increase the close time (maybe I´m wrong!):
-RC snubber.
-Two inverse-series Zener diodes (transorb).
-Varistor / VDR (some call them MOV).
-Other one?
I will appreciate if you can help me to choose and calculate the fastest snobber possible. My electronics knowledge is quite basics so simpler solutions are preferred (sorry about that!).
The only data of the solenoid valves I use is that they are 12VDC-500mA (I don’t have the tools to measure accurately the R and L of the inductance, if it is very important to know, I can contact someone that can measure it).
Thank you very much and best regards!
Tomas
The idea is that the solenoid valves must open and close VERY fast and at a rate of 10Hz max (approx.). Each valve is controlled individually and the actual valves I bought have a response time of approx. 10 ms to open/close. This is perfect to me and works fine. The problem is that as solenoid loads are very inductive so I must add a Snubber / Transient voltage suppression to eliminate the peak voltage produced when the solenoid is turned off. If I don’t use some kind of protection, surely I will fry the ICs of the circuit!
Actually I´m using one 1N4004 diode parallel-connected to each solenoid. This protection works fine but it has a big controversial issue: the close time is widely increased (by 2x or 3x) and makes my system not to work correctly.
I´ve been searching for some alternatives that don’t increase the close time (maybe I´m wrong!):
-RC snubber.
-Two inverse-series Zener diodes (transorb).
-Varistor / VDR (some call them MOV).
-Other one?
I will appreciate if you can help me to choose and calculate the fastest snobber possible. My electronics knowledge is quite basics so simpler solutions are preferred (sorry about that!).
The only data of the solenoid valves I use is that they are 12VDC-500mA (I don’t have the tools to measure accurately the R and L of the inductance, if it is very important to know, I can contact someone that can measure it).
Thank you very much and best regards!
Tomas