Voltage Regulator For Servos

Question

I need to provide external power for the servos as I'm using a lot of them. Can any one suggest any voltage regulator for the external supply of voltage and how do I connect them to the servos. Does anyone have some images of the wiring that would guide me...

Which voltage regulators shall provide the juice for the servos? I have four servos in each arm of the robot. Shall I use one voltage regulator for each arm?

jstarne1 · Answer

Hey Pranav , I am happy to help. What voltage do your servos get their max power? Some are optimized for 4.8-5 volts , 6 volts or even 7.2-7.4 volts. Once we know we can go from there. - Josh

jstarne1 · Answer

Also what battery are you using?

pranav · Answer

Hey Josh, I'll be using the servos at 5v itself. I'm using a 12v lead-acid battery.

pranav · Answer

That tutorial is really useful... But I would like to know, is it just one servo per voltage regulator or can we control mltiple servos with one regulator. I was thinking about using LM317 or LM338 which can be constructed to deliver 5v at 1.5A and 5A respectively. How much current does each servo take? Can I use those voltage regulators?

jstarne1 · Answer

@pranav , yes you can get higher amperage capabilities by connecting them all in parallel. , you can get 5 volt regulators in 5amp current capability. Then connect two in parallel to get 10amp capability. Make sense?

pranav · Answer

Sorry I couldn't follow up... My doubts are: 1) What is the amperage that the servos can take? 2) Can I use LM317 or LM338 for the external supply? If so, how many servos can I drive with each voltage regulator. 3) Major Problem: I popped out my LM1084. Would it just affect the +5V supply or wold it even affect the logic supply. If I start supplying external voltage for the servos and take the logic supply from EZ-B, would they be working without the lM1084 on the EZ-B?

jstarne1 · Answer

Servos can use different amount of current. What servos do have to power and I can better answer that question?

pranav · Answer

I'm using four servos in each arm of the robot. One each at the arm, the elbow, the fist and the claw. So the servo at the arm has more load on it to bear the weight of the remaining three servos in the hand. So it needs more juice...

jstarne1 · Answer

Here ya go , 4 - 5 volt regulators @ 5amp in parallel This will give you up to 20 amps to power lots of servos! Most high torque servos draw 1-2 amps at stall and standard servos even less , maybe 200-500 ma per servo. If for some reason 20 amps is not enough ( not likely) you can add another regulator to the same setup. Be sure and make sure you use wiring with appropriate gauge to handle the current. This calls for 10-12 gauge stranded wire. Use a barrier strip and spade crimp on connectors to connect several servos to this regulated power source. This should resolve your servo power needs

pranav · Answer

That is really very useful... Thanks a lot Josh... How about my third doubt regarding Lm1084.. Can I solve that issue?

jstarne1 · Answer

The EZB v3 onboard PIC needs the 5 volt supply , you will want to have a good 5 volt regulator on the EZB V3 for the PIC digital pins to function properly. If the regulator went bad from overloading or other problem then -carefully- replace it.

pranav · Answer

So can I go for any 5v regulator that is compatible with the pins of LM1084... How abot LM1085? It gives 5v at 3A. I know that won't be sufficient to drive all the servos from EZ-B... So can I take the LM1085 to drive only components like HC SR-04, camera, MP3 Trigger from EZ-B and the rest of the servos from external power suppy...

jstarne1 · Answer

The 3 amp regulator will work fine , just don't expect to power all your servos from the ezb , external power is the way to go for motors and servos because they are so unpredictable in their current draw.

pranav · Answer

Thank you Josh, for that quick replies... I would try that 3A regulator for EZ-B and add external power supply for the servos... I will try that today and get back to you... Once again Thanks a lot Josh...

jstarne1 · Answer

Your welcome!

pranav · Answer

Hey Josh, I have an issue... I was trying to check if the digital pins has got anything to do with the LM1084... Using the Set Digital.. I tried to read the voltage out from Digital pins. I'm reading a 7v when it is SET. I'm using a 12v battery to power EZ-B. Does it mean that the components used on EZ-B would work even without that regulator LM1084 if we supply the external voltage to each of the components. What should be the ideal value on Digital pins when they are set? @DJ , please guide me through this.

jstarne1 · Answer

Digital Pin Set ON will have a +5 volts , with a meter you should read 4.8 - 5 volts . 7 volts for a digital pin is a bit high. What voltages were your regulators putting out at that time?

pranav · Answer

I haven't placed any voltage regulator in the place of LM1084.. The other regulator is left as it is... What am I supposed to do?

jstarne1 · Answer

Test what voltage the regulator is putting out right now. It seems ver high. Is the led on the Bluetooth and main power led coming on?

pranav · Answer

Yeah both the LEDs are on, I'm even able to connect to the ARC. I checked each of the pins by Set Digital option, switching on and switching off. I read the voltage across each of the Digital pins and Gnd. When it is On, the value is 7.1-7.2V and when it is Off, it's 0-0.1V...

jstarne1 · Answer

Ok check the voltage from that regulator because 7 volts is way too high , it appears that the regulator is malfunctioning and putting 7 volts in.

pranav · Answer

I haven't connected any regulator... Moreover, dosen't the voltage to the Digital pins come from the Microcontroller? I want to know about it... I don't really know if that voltage appears from the microcontroller or the voltage regulator. There is no voltage regulator connected in the place of LM1084. I trimmed it away so that I can add a new one... An LM1085...

jstarne1 · Answer

The microcontroller does not generate the voltage it just passes through the controller from the regulator. If the regulator is putting out voltage too high the digital pin voltage could be affected. The controller is just acting as a fast on / off switch when you use the Set digital on or off feature.

pranav · Answer

Ohhhk.. But how would there be any voltage generated at the Digital pin i.e. the signal pin..

jstarne1 · Answer

Remove your Bluetooth and pic from the board at this time. It does not need to be in place to troubleshoot the regulator. I don't want you to potentially damage your pic from overvoltage. Then check the voltage from the regulator.

pranav · Answer

Okay... I shall remove them.. But i don't know from where is the voltage generated... There is no regulator in here...

pranav · Answer

I guess the other voltage regulator is for the bluetooth... So I guess it has nothing to do with the signal pins... My point of concern is if the voltage generated is from the microcontroller as there is no voltage regulator.. When I measured the voltage across 5V and Gnd, there is no voltage. I would even like to know how is the voltage across 5V and Gnd generated? I mean does this voltage regulator produce the voltage for both the 5V and the Signal pins?

jstarne1 · Answer

Measure from the remaining regulator itself and post the part number that you tested. I want to see if the remaining regulator itself is working and go from there.

pranav · Answer

I tested it without any voltage regulator. As I posted the picture, I measured the voltage on the signal pins of the microcontroller in the same state. I didn't add any regulator to it.. And still it gave voltage over the signal pins. The voltage across 5v and Gnd is 0V.

jstarne1 · Answer

Ok I understand there is a miscommunication happening here. There is one regulator on the board at this time. Any voltage on the board must come through that regulator. My recommendation is to directly test the regulator that is still attached. Probe the pos emitter leg on the regulator still on the board.

pranav · Answer

I have a doubt... We have 2 voltage regulators LM1084 and MIC29300 on EZ-B V3... I would like to know what is the function of each of these voltage regulators? I mean what is the purpose of LM1084 and MIC29300?

cosplaying_bunny · Answer

the lm1084 is to power the digital pins (like servos) and the other regulator is for the microchip ic

pranav · Answer

Thank you, then how is the bluetooth powered?

cosplaying_bunny · Answer

on the same regulator as the ic is i think~

pranav · Answer

Thank you @cosplaying_bunny , Now i knew that even my second regulator i.e. MIC29300 is also damaged... I coldn't get that regulator here... So is there any other voltage regulator that can be replaced with MIC29300 that has the same pins? Please guide me through this...

jstarne1 · Answer

Digikey.com has them and they do international mail

pranav · Answer

Here, I post the video of my problem with the voltage regulators...  I guess the problem might be the capacitors that are associated on the board to the voltage regulators... @DJ please help me out as to what are the capacitors that are connected to the VR1 and to VR2 so that I can replace them with the ones compatible to the regulators I'm using... Is it actually with the capacitors?

jstarne1 · Answer

@pranav , I took a look at the video and I will look closer later today. The capacitors are in parallel not series so they can literally be completely removed and ezb still function. So you can eliminate capacitor as being your problem. It does appear your voltage regulator setup is functioning

pranav · Answer

Yes Josh, the voltage is appearing... But the LED on EZB and Bluetooth are not glowing and the voltage between 5V and GND is 1.2V... So, I'm confused... eyeroll eyeroll eyeroll

jstarne1 · Answer

@pranav , it appears the board etchings may have been shorted out , because your barely getting voltage through them. The last component I can think of testing is the the resistors. Those are the only other inline components besides the etching that could have been damaged to cause these test results. Remove power , the chip and Bluetooth. Check the ohms of the resistors. Make sure they are within reasonable tolerance. If they have been damaged they may not allow voltage to pass through as normal. If the resistors are outside 10 percent tolerance then replace them. If they are correct impedance then it's the etching of the board thats damaged. Sidenote: if the board etching is damaged though that will prevent the function of ezb you could try soldering jumpers from ground to the ground on the IC socket and power from regulator to the IC socket. That would bypass the damaged etching in the board. That's a last ditch effort to revive a badly damaged board so follow the resistor tests first.

pranav · Answer

Ok Josh, It's the worst case scenario... I have to bypass the voltage.. Now where would the output of LM1084 go and where would the output of MIC29300 go?

pranav · Answer

Josh, What is the ground and power on the IC socket? I mean where should I connect them on board? Where should I connect them to the microcontroller?

jstarne1 · Answer

That's a great question , let me see if I can find the pin out for the pic and go from there.

pranav · Answer

Hey Josh, I found these pins on board... 5v, Gnd and Vin... Does that mean that the common ground would go there, the 5v i.e. the power for servos would go to the 5v and the input for microcontroller would go to the Vin?

jstarne1 · Answer

I'm not sure if that would bypass the damaged etching. I would probably run a power and ground to the two spots under the board that you test on. The ones directly underneath the Chip , I believe those are past the damaged etching , try applying power there and see if your electronics light up.

pranav · Answer

Josh.... Finally....... It's working... Thanks a lot for your support... I soldered the Vin directly beneath the board and the +5V and Gnd to the pins i mentioned in the picture... It's finally working.. It wouldn't be possible without your help... I'm wholeheartedly thankfl to you Josh... Finally we did it...

pranav · Answer

I really tortured that board all these days.. Now I understand the value of it... I gotta take care of it from now...

jstarne1 · Answer

Yay ! I'm glad we found the problem and found a work around to repair your EZB , I'm seriously glad because I want to see that foamboard robot you made start moving around .. Thankyou for your patience I just wanted to get you taken care of. Goodluck with Foambot 2000 ! - Josh

pranav · Answer

Thanks Josh, I shall post the project soon...

pranav

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