The striker had also been on trial at Liverpool before signing for Huddersfield Town in 2013.
The forward burst onto the scene as an 18-year-old by scoring an impressive 25 goals in one season for Dulwich Hamlet in the lower divisions.
It caught the eye of a whole clutch of Premier League and Championship clubs, and Carr ended up taking in trials at Leeds United, Liverpool and Charlton Athletic before signing on at the Terriers on a two-year deal.
However things haven't worked out so well since heading to the John Smith's stadium, with loans at League Two clubs Fleetwood, Mansfield and Dagenham and Redbridge failing to see him register significant playing time.
With his contract expiring, Richard Money has brought him to the Abbey Stadium on a two-year contract.
Can Carr impress at Cambridge?
Though the striker hasn't managed to take to professional football with the same way he managed the upper semi-pro leagues, at 21-years-old he is still young enough to find a place in the game.
Having struggled on loan for a couple of seasons, Carr will now have the chance to settle in Cambridgeshire, and work on breaking into the first team squad under Money.