I’ve met very few teams that successfully found a valuable and useful way to update and use a Sprint Burndown. The Sprint Burndown can be tedious to update (if done manually), and doesn’t seem to trigger the discussions in the Scrum team it is designed for. Even to agree on a unit causes confusion (hours, tasks, finished User Stories?).
But don’t despair; let me introduce you to Confidence Smileys. Confidence Smileys provide a simple, honest, transparent and overview-friendly tool for the team to visualize how confident a team is that they will be able to finish each User Story by the end of the sprint. The can replace the need for a Sprint Brundown (or Sprint Burnup), or function as a complement.