Let's Make Robots!


stop a capacitor charging when full

i a ma a complete beginner and i am reading a book about beam bots (mostly) and i had an idea for a beam bot which probably wont work and i might not build but i decided to try and draw a schematic anyway. the idea is it goes towards light and when there is lot of light it starts to charge a very large capacitor before going back to following light. when it detects vibration(can you get vibration sensors?) it uses the power from the large capacitor  to run until there is a lot less light ( ie it is under something) and stay until the vibration has gone.

Lots of strange Sharp IR Noise…?

Hey everyone. So, I just finished my first robot in a few years, my first being 2 1/2 years ago. This one is a lot more complicated in terms of hardware since I made my own boards and all, and have 5 ICs in one circuit. I'm done with programming and everything runs well but there's one ongoing problem with my Sharp IR GP2D120 sensor.


Hi y'all, just joined LMR, fantastic site, lovin' it already . . .


I am a bit of a beginner to robotics, I mean I can program and all that, and make these things, but I know not how or why they work.

One thing I have been wondering is about capacitors:

When designing a circuit, how does one know where to place capacitors, or why to have them, or how they function in that position?

With this circuit in particular (from here: http://letsmakerobots.com/node/2074), why the caps?

those two in the top-right, why do they both need to be there?

solar trickle charger-solar engine

Hi, can anyone help?

I am trying to make my robot battery powered with trickle charge with two solar panels.

Charge Capacitor with Solar Panel

Is anyone aware of a simple circuit that will charge a capacitor with a solar panel (Small one from calculator) and then discharge to an LED via a transistor when the capacitor get's fully charged? The point is to make the LED flash. The frequency of the flashes would depend on ambient light conditions (less light, longer charge time). The closest thing I found is the circuit bellow. Would replacing the +12V with a solar panel still make it work (just take longer to charge)? Also what is the N.C. symbol at the transistors base ?(No Circuit or Normally Closed???)

Running a MicroController off a SuperCap

Because I keep daydreaming about wiring up my house with dozens of sensors, I was wondering how hard it would be to power a micro controller (say picaxe) off a super capacitor.

A supercap is an electrolytic capacitor with an insanely large capacitance. Mine is half a Farad, 470000 uF. But is rated for only 5.5 V. That's the deal with these caps. Higher capacity at the expense of the maximum voltage they can endure. Or simply at an expense. This one costs about $4 at DigiKey.

Super Capacitor in solar power supply - a few queries

I intend to build a remote 'weather station'

The station will:

  • Be completley independant of any external power, ie, it will produce its own power via solar cell(s)
  • Measure temperature only
  • Transmit its finding over an RF link to an indoors reciever

Instead of using a rechargeable battery supply with charger circuit, i have decided to use a 35F, 2.7V super capacitor to smooth and store power.

Coil Gun Rifle

I have been making soem good progress on the Coil Gun Rifle:



Larger images in attachments.


Practical question about servos and capacitors

I have read in many places on this site about using capacitors to reduce motor and servo noise. I am now using 0.1 uF capacitors across the leads of my motors as standard practice. I'm also using 470 uF and 0.1 uF capacitors around both sides of my voltage regulator. As yet I haven't tried applying a cap to a servo, and I have a quick question.

Price: $4.95 USD
Description: Yes you read that correctly - 10Farad capacitor. This small cap can be charged up and then slowly dissapated running an entire system for hours. … Read more

Capacitor's voltage rating

Hi guys.

Do you know what the voltage rating on capacitors is? My idea is that the voltage rating is just the maximum voltage it can take before the blue smoke comes out, but i'm not sure.

thank you :) 

Where can I learn more about capacitors?

One of the things that still baffle me today is when to use and how to select the correct capacitor.

I've read through this chapter about capacitors: http://www.allaboutcircuits.com/vol_1/chpt_13/index.html

Afterwards I feel I undestand how they work, but still don't have the two most basic questions answered: