Dumbarton will take on Alloa to retain their place in the Scottish Championship after a 1-1 draw at home to Arbroath secured a 3-2 aggregate victory in their play-off semi-final.Craig Barr scored a stoppage-time winner to earn Dumbarton a 2-1 first-leg win in midweek and they made a perfect start on home soil.Tom Walsh floated in a ninth-minute corner that Dougie Hill powered home with a header to give the Sons breathing space.Arbroath, who finished fourth in League One, pulled one back in the 27th minute when Gavin Swankie finished under Scott Gallacher, but they were unable to find a second goal that would have sent the tie to extra-time.