Let's Make Robots!

Make a reusable robot base / power suply in 5 easy steps

Every now and then I want to test a circuit or a new sensor or even some new idea for code but I don't have a starter kit or anything. While shopping for some robot parts I had an idea for a simple base that could be my equivalent of a starter kit, a power supply and a small robotic platform. This is what I came up with in 5 easy steps.


Step 1:



Buy a small breadboard, three 2xAAA battery holders and a couple of minature servo's, set up for continuous rotation. The battery holders are almost the same width as the breadboard.


Step 2:



Peel off the backing on the breadboard to expose the double sided tape backing. If your breadboard is a different brand then you may need to put on some double sided tape.


Step 3:



Read through this instruction carefully and note orientation of all parts before you stick them on as it is hard to peel them off again without wrecking the double sided tape. Stick on two of your battery holders, one either end with the solder lugs all on the same side. Notice that the servo drive shaft is not centre, make certain you put both servos the same way around. On the end closest to the servo drive shafts hot glue the third battery holder. Make sure the solder terminals of the battery holders are all on the same side. In the space in the centre put in a small piece of wood or plastic that you can later put some self tapping screws into.


Step 4:



 Solder all your battery holders together in series, fit the batteries and screw a piece of thin wood or plastic into the centre piece. This is your skid pan, as well as stopping the batteries from falling out you can use hot glue to attach skids to level it out. I copied Fritz's idea from one of his little robots and used a cutdown table tennis ball. 


Step 5:



 Plug in you power supply components. I've used a low dropout regulator so that I get good regulation even if my batteries drop down to 5.5V. I'm using rechargeable batteries so I get 7.2V. Because this voltage is a bit high for servos I'll put 3 diodes in series with my battery for the servo supply. I don't recommend alkaline batteries or rechargable alkalines because they have a higher internal resistance and any voltage spikes will be bigger. You will also need to drop the voltage more for your servos as you will have a 9V supply.


 That's it you now have a flexable, reuseable robot platform / power supply. The picture below is me using this as a power supply while I experiment with my MkII laser range finder. I've remove the wheels and skid pan so it sits flat. You can see the diodes used to drop my 7.2V down to under 6V for the servos.



 Good luck and enjoy! :)




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WTF!?! This is a (nice) Tip/walkthrough!

Why is is posted as a blog entry? Please re-post, so it will show up to those in need :)

Sorry if "the devisions" needs more clear explanation, I may have to have a look at that :/

Glad you like it but... How do I re-post?

I've only been here 2 or 3 weeks, I've only just worked out how to link full size pictures to 500x500 pictures and my attempt to set up an account for uploading video swamped me with so many spam emails (117 of them) that I couldn't find the email needed to authenticate the acount.

Please give me instructions on how to repost or if you have the ability as administrator please feel free to do so.

Hang on, I think I have it.... :/

Will make instructions one day soon, I hope :) It seams that many do not find it all intuitive in the beginning.. Nor do I :) Will look at it one day soon, promise :)

Nice walkthrouh. I should really use that setup. Makes it easy to get started on experimenting with different devices.

 I have a few questions:

1) Why the 1K resistor? What does it do? Doesn't that just drain the battery? 

2) I allways thought servos "like" 6V. So why the 3rd diode?

I'm not very good with electronics so forgive me if I ask obvious things, but then: there are no stupid questions right? 

1) The diodes only drop voltage if current runs through them. The 1K resistor draws about 6mA, not enough to flatten the batteries quickly but enough to stop the voltage getting too high when the servo's are first connected.

2) When I measured the voltage on my batteries after they were charged the voltage was closer to 8V thus the third diode.


I'm thinking of trying another regulator for the servos since they get a bit twitchy. Same problem you had with your object tracker. I know this doesn't happen if you use seperate battery packs.


You might have a look at these http://www.dimensionengineering.com/DE-SWADJ.htm

They are a bit expensive, but I think there worth it. Haven't gotten round to getting one myself yet. 

Those regulators are DC-DC converters. they are great when a normal regulator e.g. a 7805 would get hot.  

I use DC-DC converters on BoozeBot for efficiency. E.g. when a 5V device draws 100mA through an ordinary regulator and BoozeBot is 24V then 19volts is dropped across a normal regulator. Power is volts x amps so a standard regulator would waste 19Vx0.1amps = 1.9W as heat to supply 0.5W of power.

A DC-DC converter is about 85% efficent so only 15% of 0.5W =0.075W would be wasted as heat.

With this base and the current likely to be drawn, the expense of those regulators isn't warrented.