Going to all the trouble to seed your lawn means you don't want your new grass to die just because you have to go to work and can't water it. Grass seed and new seedlings need consistently moist soil, where the top 2 inches of soil don't dry out. When the weather's warm, this could require watering your lawn several times per day. If you can't be there to turn on the sprinklers, use a hose-end timer to turn on the water for you.
Determine your sprinkler layout. Buy several of the same sprinkler types and spread them out over the seeded area. Connect them with garden hoses, then connect one hose to an outdoor faucet. Place several small jars around the seeded area. Turn on the water and let the sprinklers run for at least five minutes, then turn them off and compare the amount of water in each jar. Move the sprinklers as necessary to ensure all jars get about the same amount of water, then remove the jars.
Add batteries to the hose-end timer and close the waterproof lid securely, or plug in the timer, as necessary. Unscrew the hose from the faucet, and attach a hose-end timer to the faucet. Attach the hose to the other end of the hose-end timer, making sure all connections are tight with no leaking water.
Program the timer to water the grass seed at your desired times, following the manufacturer's instructions. Digital timers might allow you to pick certain times of day to water, while other types of timers might let you set the length of time between waterings, such as every six hours. If it's hot outside, you might need to water more often; but if the grass is shaded most of the day, it might need water just a couple of times while you're at work.
Set the duration for each watering on the timer. Clay soils that hold water well might need only 15 minutes of water several times per day, while soils that drain better, such as sandy soils, might need 30 minutes or more at each watering. Test this by digging into the soil about 2 inches with a screwdriver after every five minutes of watering to see if the soil is damp below the surface.
Make sure the timer is turned on before you leave for work. Turn on the water at the faucet; the timer will keep the connection closed and only release water to the sprinklers at the programmed intervals.