# Solving Voltage Drop Problem on Robotics Project

• robotnut
In summary, the conversation discusses a voltage drop issue with a robotics project powered by a 4.8V NIMH battery. Suggestions to solve the problem include adding a capacitor to the power cable, using a Schottky diode, modifying the software, or using a higher voltage battery. A formula for calculating the necessary capacitance is also provided. Ultimately, the individual decides to use a lithium polymer battery with a voltage regulator.
robotnut
22 Dec 2009 21:16 Voltage drop question
Hi All;

Total noob, first post

I'm working on a small robotics project. I have an embedded computer (5V) and 2 motors with a controller. It's all powered from a 4.8V NIMH battery.
The problem I'm having;

As the battery gets somewhat tired and I load the motors for starting or climbing a steep obstacle, the voltage drops a little from 5V to about 4.5 momentarily but it's just enough to restart the computer.

What I'm thinking of to solve this problem is adding a capacitor to the power cable of the computer. Would that help the problem? Like I said the drop only happens for a fraction of a second.

I know I could use a bigger battery but I have a room issue already as it is.

You would need to give the currents of the motors and the computer.

If you just put a capacitor across the power supply, it would discharge into the motors when they turned on. You would get some benefit if the capacitor was large enough, though.

If you could operate the computer with 4.65 volts, this diagram shows a way that might help.

Using a Schottky diode, you could charge a capacitor which would then discharge only into the computer and not into the motors. Schottky dides have a drop of 150 mV (0.15 volts), so the 4.8 volts from the battery would drop to about 4.65 volts, but it would hold this voltage for short periods if the battery voltage dropped.

Could you modify the software so that the motors are always soft-started (progressively, not suddenly). Alternatively, try putting low-value resistances in series with the motors. Clearly if these are too big the motors will no longer work, but it might be worth trying.

I don't know what processor your using, but most modern ones have a large operating range (ie 3V - 5.5V). I'd check the part number on you processor and look up it's data sheet. Most likely, the operating voltage range will be listed in the first two pages (under features).
.
Most likely, your drop out is caused by an overly protective reset chip. These little three pin chips measure the voltage and reset the processor when it dips. The beauty part is that for a given reset part number, the there are any number of voltages that are available - most from Digi Key.
.
. Best Luck, keep me updated,
.
. - Mike

I = C dV/dT, and dV in your case is 0.5v. Plug in your values to calc. your min. cap. size.

For 1 A, 1 second and a max 0.2v difference you'd need 5 F.

Thanx for all the help, I did a cheap fix. Went with a 2 cell 7.4V 1000MAH lithium polymer battery with a 5V voltage regulator...

## 1. What is voltage drop and why is it a problem for robotics projects?

Voltage drop is the decrease in voltage that occurs as electricity travels through a wire or circuit. It is a problem for robotics projects because it can cause errors in the performance of the robot or even damage to the components.

## 2. How can I identify if my robotics project is experiencing voltage drop?

You can identify voltage drop by measuring the voltage at different points in the circuit and comparing it to the expected voltage. If there is a significant difference, then voltage drop is occurring.

## 3. What are the common causes of voltage drop in robotics projects?

The most common causes of voltage drop in robotics projects are using wires that are too thin for the amount of current being carried, loose connections, and long wire lengths.

## 4. How can I solve voltage drop in my robotics project?

There are several ways to solve voltage drop, including using thicker wires, minimizing the length of wires, and ensuring all connections are tight. You may also consider using a voltage regulator or adding additional power sources.

## 5. Are there any long-term solutions for preventing voltage drop in robotics projects?

Yes, there are long-term solutions for preventing voltage drop, such as using high-quality wires and components, regularly checking and maintaining connections, and designing the circuit with voltage drop in mind.

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