7805heatsinkpower supplysensorultrasound
I will be using Ultrasonic sensor HC-SR04 in water level measurement. I will be triggering the US sensor and getting back the time-pulse from it at very slow rate maybe once every minute. I want to know is it OK to keep the US sensor module powered-up at +5V using 7805 regulator continuously 24/7? Will it heat-up the sensor or its electronics and cause accuracy problems after few days of continuous operation?
The regulator should have thermal limiting (check the data sheet for details), and will shut down if the temperature gets too high. It won't damage any other parts, and definitely won't melt any solder!
Using a larger heatsink will reduce the temperature, of course. A switching regulator will be a lot more efficient and will just get slightly warm.
The problem with hobby related solutions is documentation is limited and not spec'd like commercial components or modules.
It is possible that it may work but make a block wiring diagram and consult with the OEM is advised. Mind you I don't know if they have adequate support for your question as these are built in China.
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It appears that your ultrasonic load is TTL so there is no problem switching 5 at the same time with a BEC, but I wonder if you have considered the effects of crosstalk on firing all at the same time. They indicate a 15deg detection angle but this would depend on the reflection angle of objects you wish to detect. There may be phasing issues with reflection cancellations like having 5 tweeters directed in a room. Reading the response of each echo in parallel with a time interval count won't be a simple textbook result with non-smooth objects with 5 senders.
YOu can test your orthogonal array design with any signal pulse generator and look at the signal on a parallel port logic analyzer or scope to ensure what you are design will work.
Power drive is the least of your concerns from these low power devices. Noise avoidance from conducted and radiated sources will be paramount and design of the transponder array must come first. I would spend some time on testing this part 1st to identify all the electrical, physical, acoustic, EMI, thermal, vibration both conducted and radiated sources of interference and how each affects your SONAR expectations with different objects. Will it be microphonic with vibration or loud pulse noises. How well does it reject other ultrasound sources of noise? Will the TTL Echo output change in pulse width with signal strength or just the delay time.
Will you get echos from the wrong sender due to corner refection effects.
Best Answer
Yes, a 7805 would be acceptable for powering the HC-SR04. It only requires 15mA which is not much. The trick with voltage regulators is to not run too much power through them.
Find the max power dissipation of the 7805, if you can't find it then 250mW or 500mW might be a good place to start.
Lets say you have 12V going into the regulator, that would be a 7V drop. At 15mA, this would be 7V*15mA = 100mW which would be ok (you can't go over the number or the 7805 will get too hot)
24V would be a 19V drop, and 19V*15mA would be 285mW which might be pushing it for some regulators.
Make sure you use input and output filter caps.