I installed a power feed system on my Woodland Mills HM122 Sawmill. This video details each component of the system. The total cost was approximately $325.00 including the battery. I will provide affiliate links to each of the parts below.
Please keep in mind that this probably makes the machine more dangerous and I do not recommend this be replicated. Also, it has more parts that could fail and put a stop to milling for the day.

Throttle Actuator: https://amzn.to/3yon9D0
Roller Chain x2: https://amzn.to/3kXzRFN
Idler Sprockets x2: https://amzn.to/3JsKw4F
Speed Controller: https://amzn.to/3T3RsZ0
Rocker Switch: https://amzn.to/3ZCSg9V
Limit Switches: https://amzn.to/41ZtNNz
12g Wire: https://amzn.to/3YAUIwf
Drive Sprocket for Jazzy motor: https://www.ebay.com/itm/133965882637
Motor: Pride Jazzy Select Left Side

If I were to do it again, I would definitely get a motor other than the Jazzy Select due to the mounting configuration. That would require a drive sprocket that may be different than in the previously provided link. I would also consider getting a 1" actuator rather than 1.2 because then my spacing may have been correct on the throttle without cutting a relief in the bracket.

I learned about the design of this auto feed system by watching videos from the following channels:
Mike Festiva’s Channel:    / @mikefestiva  
Jerry from Bigelow Woodcraft: https://www.youtube.com/@JerryBomay/a...
I did also reference Kevin the Miller's setup on his HM126 at    / @kevinthemiller9003  



Disclaimer:
This video is for entertainment purposes only. The activities performed within this video should not be recreated. In no event shall Nick’s Next Project be responsible for any injuries or damages occurring after viewing this content. Statements made within this video are merely opinions and should not be taken as facts. The opinions expressed in this video do not reflect or represent the view or position of any external organization, group, or agency. Always heed the advice and guidance of a professional in person before proceeding with your project.