Re: the best power regulator
 

This thread hasn't really addressed the original posted question and it has a important direct bearing on First and next year's game. There has been allot of posts on CD this summer concerning coprocessors. Seems allot of teams are looking to add coprocessors to manage additional sensors. They are going to need power from the robot.
Is there a better regulator than the 7805 series for 12 volts that is easy to use and readily available? In other words can a reference design be suggested that world work well and avoid most pitfalls.
Since it seem that there maybe allot more teams actually using additional electronics, are the advantages to using the 7.2 volts from the back up battery worth having First consider opening up that source for additional electronic? This also applies to the use of a separate battery for electronics that the original poster may consider using. Is it worth it? As Al pointed out the use of a non LDO regulator has some problems. Then that brings up the subject of is there a good reference design for using a LDO regulator for the 7.2 volt supply? I know Power supply design is a complex topic and the details can be debated around and around. May be those with the knowledge and experience could jump into this thread and help with some reference designs and guide lines to avoid pitfalls.

Re: the best power regulator
 

To give better power supply design details, the requirements need to be specified:

1. how much current is required on the 5V line?

2. how much ripple or noise is acceptable?

3. is effeciency important for the application?

4. how much room is available for the regulator?

5. must the design be limited to through-hole componets or can the design implement surface mount parts (which you might not be able to solder by hand)?

6. are you making a printed circuit board or are you going to assemble the parts on a proto-board?

there is no one-size-fits-all 'best' voltage regulator circuit.

Re: the best power regulator
 

Add to Ken's list...
reserve power needs, input voltage (some devices can provide 5 volts from a single "D" cell) effects from stray magnetic fields (some use multi winding coils and high frequency oscillators) and location for cooling if needed.

As Gdeaver has stated LDO (Low Drop Out) voltage regulators are available. If money is no object then anything is possible. However, using a good 7.2 volt source and a couple of diodes get you down to almost 5 volts too, 3 x 0.6 volts = 1.8 volts with no current drops. If the current load always stays the same a current source can be assembled using a FET and resistor

Re: the best power regulator
 

1. less then 200mA

2. as little noise as possible i will just be using normal TTL ICs

3. as efficient as possible, but effeciency for what? voltage?

4.as much room as as needed

5. through hole components

6. probaly a bread-board to test it then finalize it on a printed circuit board

Re: the best power regulator
 

also I AM NOT GOING TO USE IT WITH THE RC IF I DO, IT WILL BE WITH AN OLDER PBASIC ONE WHICH RUNS STRAIGHT FROM 12 VOLT BATTERY SO PLEASE STOP SAYING I CAN DO IT WITH THE RC!!!!!!!!!!!!!!!

Re: the best power regulator
 

You know, a lot of people have put time in responding to your request that was not very well outlined, and you show very little appreciation to them despite the fact that they took time to respond to your post. I've noticed this is not the only post of yours that you have given a response like this. This forum is about FIRST robotics, not your special robot, so how can you fault them for assuming you are going to use the RC. Furthermore, who are you to say that they can not discuss how to implement this for the RC, which the majority of the people reading this forum would benefit from. Yeah, its not completely centered on topic, but its still related to the original post, and the discussions here benefit a much larger group of people than just yourself.

Also, caps are considered "screaming" online, and it is pretty rude to use them.

Just my $.02.

Re: the best power regulator
 

]

in this case the 7805 circuit already discussed is going to be the best approach.

efficiency measures how much power is lost or waisted. You normally only worry about efficiency if you are using a lot of power, or if you are running off batteries and really need to maximize battery life.

in this case, if you are dropping from 12V to 5, and drawing 200mA, then you are putting in 12*.2 = 2.4W and getting 1 watt out (5 * .2)

so this example is 1 / 2.4 => 42% efficient. Not great, but if your whole system is drawing 100 watts, or a 1000 watts (like a robot) then the lost 1.4W is not significant.

If you used a switching power supply instead you can get 90% efficiency or better, but the design is more complex, has more parts, and costs more.

Re: the best power regulator
 

No specifics yet, so I describe a compressor setup we may use next year. Maybe everyone can critique it. We have a chip carrier board with the following.
1. A 7805 TO220 regulator non heat sinked.
2. A 10uf aluminum 16v cap on the input.
3. A 100uf aluminum cap on the output.
4. A MAX232A chip with bypass cap
5. A PIC 18F452 microcontroller with bypass cap.
6. 2 LEDs 20 ma each.
We have used the following senor chips - A analog devices gyro, last years accelerometer, a digital compass, a SRF04 sonar, a sharp IR ranger, and the hitec servo powered by the 5 volts. We have had up to 3 sensors at a time plus the servo. We have run it off of a 7.2 volt wall wart and a 7.2 volt 1800mah hobby nicad pack. Everything hardware wise is working fine. The set up has run for days and the regulator is just slightly warm. The total load max is < 350ma. Never ran it on 12 volts. So the question is what should be done for heat sinking? Is there something else that should be added to protect it from the robot battery? Spiky noise from the motors etc. What about fusing? What are the issues with the rs232 cable and the grounds. I a hobbyist not an EE so simple answers, don't assume to much. From what we have so far coprossesors look like a good way to extend the auto mode with out running into interrupt hell and other programing issues with the FRC.