... Basically, I have an assembly line at work and I need the workers to be conscious of how many units they are putting out every minute. ...
Excellent description of what you want to do.
Personally, I don't believe a timer is going to be very useful as an aid to production. You need something that counts the number of units completed every minute, providing the worker with a running display average of the rate of completion. For each unit completed, a counter is incremented either by the worker or by a sensor on a conveyor belt. To display the rate of completion, you divide the number of units by the elapsed time in minutes, a job for a microcontroller which will also display a running average of the rate of completion on a digital numeric display.
By running average, I mean you accumulate a certain number of unit counts, say ten units, and divide by the time elapsed from the first unit to the tenth unit thus displaying the average completion rate per ten units. Display this result. Then for the next completed unit, you divide by the time elapsed from the second unit to the eleventh unit and update the display. And so on for each subsequent unit, thereby computing a running average that is updated and displayed for each unit completed but is averaged over the last ten units. There is nothing magic about computing the running average over the last ten units completed. Pick any number, including as little as one unit. The important thing is to make the action that increments the unit counter as unobtrusive to the assembly process as possible. It is also important to use an accurate timing source to avoid cumulative timing errors. An RC timer is not the best choice for this.
There are geared synchronous clock motors operating from the power line frequency available that rotate their output shaft at one revolution per minute. Attach a cam and a microswitch to illuminate an LED or sound a buzzer or whatever once each minute. These are a bit pricey if purchased new, but you may be able to find an inexpensive one on Ebay.
Perhaps the simplest incentive to maximum production rate is an analog clock with a sweep second hand mounted next to a totalizer that counts the units completed. The worker can easily relate their production rate to elapsed time after a little practice. It helps to offer a bonus for number of units completed above a minimum rate, although this can also cause quality problems if a worker falls behind the target rate and attempts to play catch up. Solve this by setting reasonable minimum rates of production.
Good luck supervising and motivating workers on an assembly line. I would rather try herding cats.
