The description of the OpenEVSE says that it can control two relays, but in most images an videos I see that the power to the relay block is just one pair of cables (12V and 0V), so there is not actually a relay test taking place.
Also if there were two relay outputs, how do you perform a relay test? Even if you turn only one relay at a time, any one J1772 plug terminal pin would get live 240V with respect to Ground, not really safe.
AM I missing something?
OpenEVSE can power either 2 SPST or 1 DPST relays. DPST is more popular. The relay is cycled only if the Auto detect service level is set for countries that use split phase.
0 hots detected NO GROUND Error
1 hot setected Level 1
2 hots detected Level 2
Stuck Relay test runs continuously whenever the relay is open. Ground test runs continuously whenever the relay is closed.
The test feature for ground does intensionally leak a very small current to ground. Turn one relay on and read AC detect chips then turn the other on and read the chps again.
See the flow chart attached
'The test feature for ground does intensionally leak a very small current to ground.'
The current for the ground test is not that small - about 5.5mA. The total ground drain current for this circuit is 11mA. In addition, the type of resistors selected with a nominal value of 22kOm do not meet safety requirements. I see resistors on the board with a valid operating voltage of 200-250VAC.Creepage PCB is also critical
@Vitaly. The information you post is not accurate, 22k was used in very early OpenEVSE boards with MID400 AC detect chips in the USA with 120v split phase. 47k was used for 230v.
The current version of OpenEVSE uses HCPL2731 opto-isolators with 330k ohm resistors and N4004 diodes. At 240v AC the leakage is 0.73ma blocked by the diode half of the time.