11/17/2023 0 Comments Ryobi zero turn mowerThis means it will need something on the order of 2-4k ohm resistor in series to drop the voltage enough to make it effective (I did not have that and observed it had like a 15-20 second on/off delay). In addition it cuts out at an even lower voltage, something on the order of 10v. The problem with it is that cuts in at some very low voltage, significantly lower than the 48v for which it is rated. I like the second relay 'cause it has a coil resistance of about 1.25k ohms. As I said, the grass is getting long and the wife unhappy. It is a 48v SPST relay, I experimented with it, but alas did not have on hand the resistor I'd likely need to make it work. The relay has a coil resistance of 86 ohms so the 250 ohm resistor makes the voltage across the relay max out at about 52 * 86 / (86+250) or about 13.3 volts.įWIW I was hoping to use this relay instead of the DPDT one linked above. With that relay you probably don't want to change the 250 ohm resistor much. With that said, the parts I used are these: I put three in parallel for the "200 ohm" part (making 167 ohms) and two in parallel for the 250 ohm part that feeds the relay. In my build I actually used 167 ohms 'cause I was cheap and ordered a 10-pack of 5w/500 ohm resistors. One other thing: in the above I show a 200 ohm resistor for the pre-charge leg. I am sure there is an elegant solution but I'm tired of working on this, the lawn has gotten too long. If you turn off the mower and then turn the key back on again prior to the relay turning off the capacitors in the mower won't have been brought back up to voltage and instead the contactor will immediately engage, look like a short to the battery, and the battery's BMS will shutdown. The astute here may recognize a problem that I did not pre-think and rather found during testing. When I turn off the key the mower shuts down immediately and then about 3-5 seconds later I can hear the relay that I added disengage. I've wired this up and there is about a 3-5 second delay after I turn on the key until the mower's contactor "clunks" into place and turns on the mower. you will notice that Ryobi has one across the contactor relay coil). The purpose of the diode is to prevent the closing of the contactor from keeping the relay engaged (the other diodes across the relay coil is just good practice to keep the collapsing field of the relay from sending a reverse voltage spike into the circuit. When the key is turned on it slowly brings the capacitors up in voltage and eventually it reaches a level where the relay can fire. In my wiring the key enables a path through a resistor (plus diode) that goes to the mower side of the contactor. I disconnect the later and run it through a relay so that the 48-to-12v only gets turned on when the relay closes. The key has 48v (52-56 actually with the LiFEPO4 batteries) on one side and that enables a path to the 48-to-12v converter. I don't know that the actual circuit in the mower is the way I have it above, it is just my way of thinking about it. It seems that the key enables a 48 to 12v converter which then turns on the contactor relay. The idea of the circuit above is to use the capacitors in the mower to delay enabling a relay turning on and off the contactor in the mower. Finally enough stuff came together that I was able to complete this seemingly endless project.
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