Gated clock pulses

I would like to produce short bursts of clock pulses (about 6 or 8 pulses of a 40KHz clock every tenth of a second). I know how to use a 555 to produce a gate pulse every tenth of a second that is the correct duration, but how would I synchronize the circuit so there is not a transition in the middle of a clock pulse?

Essentially you don't, and why would it matter?.

Best solution is to program a PIC to do it, an 8 pin PIC is the same size as single 555, and will do it much more accurately with less components.

Presumably you're wanting to generate IR remote pulses?.

Actually it is for an ultrasonic transmitter. Will a PIC generate accurately timed 40 KHz pulses to properly resonate the transmitter? One cycle makes a difference of about 8.6 mm travel time. I would like a consistent measurement which means I would like a complete pulse at the beginning of the pulse stream.

The other consideration is that the circuit runs off of a 9V battery and I need the battery to last as long as possible. The pulses are not always on, so I need as low of a power draw as possible in its quiescent state.

DSG

DSG said:

Actually it is for an ultrasonic transmitter. Will a PIC generate accurately timed 40 KHz pulses to properly resonate the transmitter? One cycle makes a difference of about 8.6 mm travel time. I would like a consistent measurement which means I would like a complete pulse at the beginning of the pulse stream.

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Same thing, IR copied the existing frequency from ultrasonic remotes.

A PIC will generate far MORE accurate 40KHz pulses than a 555.

The other consideration is that the circuit runs off of a 9V battery and I need the battery to last as long as possible. The pulses are not always on, so I need as low of a power draw as possible in its quiescent state.

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PIC's are also EXTREMELY low consumption devices, with various included features for further reducing current drain.

PIC it is then. Thanks for the help.