My comp buggy gets alot of testing done to it since I just caint leave anything alone for more than a few weeks. After the last comp I made some pretty drastic changes to it in hopes of being able to keep it up with the rest of the competition out there.
One of the things I did was switch to an 11.1V LiPo battery. I did this to lower my center of gravity, lighten the buggy overall, and to give me more punch when I need it.
Ever since I have been running this buggy I have had a Mamba 25 in it from Holmes Hobbies and it has worked great. However, the BEC is pretty weak so I had my steering servo wired directly to the main battery for power while running my dig servo off the Mamba's BEC. With the switch to 11.1V a new setup was neeeded so follow along as I install a voltage regulator to power my servos.
First thing is to solder a connector to the ESC side of the battery plug. I have lots of burned up servos so I just cut the wires and connector off of one. I snipped the yellow signal wire flush with the connector but it wouldn't hurt to just remove the pin.
Here you can see the servo power connector soldered to the male Deans plug .
Next thing you want to do is remove the BEC power wire from the Mamba's receiver plug. You could just cut this wire but I don't like to make permanant changes because I never know when I might want to change things again. Using a hobby knife GENTLY pry up the small plastic lock tabs and remove all three wires from the connector. Be sure to note the order of the wires before you remove them since not all receivers have the same pin positions.
Now cut a length of heat shrink and slide it over the wires. Then fold the power wire back under the heat shrink, be sure that the heat shrink is long enough to fully cover the connector. You don't want anything exposed that might cause a short.
Reinstall the Ground and signal wires into the connector. The finished product should look like this.
Now you are ready for the voltage regulator. I chose to use the MPI ACC234 Heavy Duty Regulator. This sucker is pretty big but it has some really nice features that make it worth it. No it doesn't come with the TLT chassis spacer zip tied to it.
1) A resistor pot allows you to adjust the output voltage.
2) It is rated for 20 watts of power dissapation. (more on this later)
Plug the female connector from the voltage regulator into the power tap on the ESC.
Plug the male connector from the voltage regulator into the slot on the receiver marked (B) or (batt). Before doing this plug a fully charged main battery into the ESC and use a voltmeter to check the output of the voltage regulator at the male connector.
Plug in the ESC to the channel 2 position of the receiver.
Here is what the system looks like outside of the rig.
Here is the system installed in my buggy. The steering servo is plugged into the channel 1 position and the dig servo is plugged into the channel 3 position.
The instructions say that it is designed for 5 cell NiCd/NiMH and 2 cell LIon RX packs but MPI told me that as long as the 20 watts is not exceeded the regulator will be fine.
So what does 20 watts mean?
With an input of 7.2V, and an output of 6.0V; it can handle 16.6 amps of current draw from the servos.
With an input of 11.1V and an output of 6V; it can handle 3.9 amps of current draw.
To calculate this you need to know the voltage drop across the regulator. That is found by subtracting the output voltage from the input voltage [input(V) - output(V)], then divide 20 by that number.
Current(amps) = 20(watts) / voltage drop(V)
For my setup: voltage drop = (11.1 - 7) = 4.1V then current = 20 / 4.1 = 4.88 amps
If I want to draw more current I have to raise the output voltage to be closer to the input voltage. However, the output voltage must always be at least 1V less than the input.
Recommendations:
1) If you want to push your components to the limit running an 11.1V input voltage then I would recommend running 7V output to the servos. This will give you the ability to pull 4.88 amps, which should be good for running a single high torque servo, and some cushion for when the battery is freshly charged. Running servos on 7 volts is pushing it for alot of servos, I have had good luck running Hitec servos at 7-8V but not JR's.
2) If you want to play it safe then I would recommend running a 9.6V input voltage. This way you can set the output voltage to 6 volts and have about 5.56 amps for the servos. This would be a pretty safe setup for rigs that get pack after pack run through them continuously.
3) Absolutely no worries if you run this on 7.2 - 7.4V with an output of 6V.
Because this is a competition buggy I try and push the lightest components as hard as possible since it does not usually see extended use.
If you do this mod your ESC will thank you by running cooler and being more stable.
As I found out, pumping 11.1V into the Mamba 25 while asking it to run the dig servo was really pushing it to the limit; and this was only a Hitec HS-81MG. The little ESC took the abuse but ran very hot and would thermal shutdown if I engaged the dig for very long.
With this setup, testing over the last couple weeks has shown the Mamba runs cooler and should live a happier life. So far I have had no problems with the voltage regulator.
Happy crawling.
Links:
Get your voltage reg, ESC, servos, and motors at:
Holmes Hobbies
MPI links:
MPI voltage reg
ACC-234 instruction sheet
One of the things I did was switch to an 11.1V LiPo battery. I did this to lower my center of gravity, lighten the buggy overall, and to give me more punch when I need it.
Ever since I have been running this buggy I have had a Mamba 25 in it from Holmes Hobbies and it has worked great. However, the BEC is pretty weak so I had my steering servo wired directly to the main battery for power while running my dig servo off the Mamba's BEC. With the switch to 11.1V a new setup was neeeded so follow along as I install a voltage regulator to power my servos.
First thing is to solder a connector to the ESC side of the battery plug. I have lots of burned up servos so I just cut the wires and connector off of one. I snipped the yellow signal wire flush with the connector but it wouldn't hurt to just remove the pin.
Here you can see the servo power connector soldered to the male Deans plug .
Next thing you want to do is remove the BEC power wire from the Mamba's receiver plug. You could just cut this wire but I don't like to make permanant changes because I never know when I might want to change things again. Using a hobby knife GENTLY pry up the small plastic lock tabs and remove all three wires from the connector. Be sure to note the order of the wires before you remove them since not all receivers have the same pin positions.
Now cut a length of heat shrink and slide it over the wires. Then fold the power wire back under the heat shrink, be sure that the heat shrink is long enough to fully cover the connector. You don't want anything exposed that might cause a short.
Reinstall the Ground and signal wires into the connector. The finished product should look like this.
Now you are ready for the voltage regulator. I chose to use the MPI ACC234 Heavy Duty Regulator. This sucker is pretty big but it has some really nice features that make it worth it. No it doesn't come with the TLT chassis spacer zip tied to it.
1) A resistor pot allows you to adjust the output voltage.
2) It is rated for 20 watts of power dissapation. (more on this later)
Plug the female connector from the voltage regulator into the power tap on the ESC.
Plug the male connector from the voltage regulator into the slot on the receiver marked (B) or (batt). Before doing this plug a fully charged main battery into the ESC and use a voltmeter to check the output of the voltage regulator at the male connector.
Plug in the ESC to the channel 2 position of the receiver.
Here is what the system looks like outside of the rig.
Here is the system installed in my buggy. The steering servo is plugged into the channel 1 position and the dig servo is plugged into the channel 3 position.
The instructions say that it is designed for 5 cell NiCd/NiMH and 2 cell LIon RX packs but MPI told me that as long as the 20 watts is not exceeded the regulator will be fine.
So what does 20 watts mean?
With an input of 7.2V, and an output of 6.0V; it can handle 16.6 amps of current draw from the servos.
With an input of 11.1V and an output of 6V; it can handle 3.9 amps of current draw.
To calculate this you need to know the voltage drop across the regulator. That is found by subtracting the output voltage from the input voltage [input(V) - output(V)], then divide 20 by that number.
Current(amps) = 20(watts) / voltage drop(V)
For my setup: voltage drop = (11.1 - 7) = 4.1V then current = 20 / 4.1 = 4.88 amps
If I want to draw more current I have to raise the output voltage to be closer to the input voltage. However, the output voltage must always be at least 1V less than the input.
Recommendations:
1) If you want to push your components to the limit running an 11.1V input voltage then I would recommend running 7V output to the servos. This will give you the ability to pull 4.88 amps, which should be good for running a single high torque servo, and some cushion for when the battery is freshly charged. Running servos on 7 volts is pushing it for alot of servos, I have had good luck running Hitec servos at 7-8V but not JR's.
2) If you want to play it safe then I would recommend running a 9.6V input voltage. This way you can set the output voltage to 6 volts and have about 5.56 amps for the servos. This would be a pretty safe setup for rigs that get pack after pack run through them continuously.
3) Absolutely no worries if you run this on 7.2 - 7.4V with an output of 6V.
Because this is a competition buggy I try and push the lightest components as hard as possible since it does not usually see extended use.
If you do this mod your ESC will thank you by running cooler and being more stable.
As I found out, pumping 11.1V into the Mamba 25 while asking it to run the dig servo was really pushing it to the limit; and this was only a Hitec HS-81MG. The little ESC took the abuse but ran very hot and would thermal shutdown if I engaged the dig for very long.
With this setup, testing over the last couple weeks has shown the Mamba runs cooler and should live a happier life. So far I have had no problems with the voltage regulator.
Happy crawling.
Links:
Get your voltage reg, ESC, servos, and motors at:
Holmes Hobbies
MPI links:
MPI voltage reg
ACC-234 instruction sheet
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