I am newbie and I want to build a project that contains two linear actuator that move synchronously. Two of them will lift up and down at same time. I use arduino mega and VNH5019 motor driver. I have thompson electrac ELD linear actuator. I have never tried to synchronize two linear actuator. Linear actuator have encoder output ( it is hall effect encoder -( not absolute. So it cannot keep last position in case of power cut )). Encoder type is hall effect type. Encoder output voltage levels low (logical zero), typical / max is 0.1/0.25 Vdc. Also it has output fully extented/retracted signal. I tested it with H-Bridge motor driver made of 4 SSR relays and push button switches to retract and extract. There is a synchronization problem.The system will stop when actuators extracted 500 mm ( actuators have 900 mm stroke length) How should I solve that synchronozation problem could you help me ? What should I do?

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It sounds like you need to watch both encoder outputs and don't let one get ahead of the other. Naturally, they won't sync exactly (i.e., pulse simultaneously) but you can set a limit on how many counts to let them differ by, before pausing the faster actuator while the slower one catches up.

If you need to save positions across a power failure, you'll need to 1) provide enough backup power to keep the system alive past the supply failure to give you time to stop both actuators and store both of their positions in EEPROM; and 2) provide a signal to the Arduino that the supplied power (not the backup) is going down, so it can begin its orderly shutdown.

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