Let's Make Robots!

Questions about my hacked RC car arduino robot

Greetings everyone. I have an old RC car with 6V accumulator. Can I power my arduino board + the l293d motor driver from this accu without using any voltage regualtors? I read that arduino and 3 of the 4 pins on the l293d motor driver require 5V. 

The voltage requlator I have requires 2.5V more ie 7.5V, but the accu is 6V. More stupid questions will follow :D

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You can stack your h-bridge chips like Elijiah did, or you can buy an high power motor controller like this one (overkill, perhaps) OddBot designed, or you can build you own like any listed in this h-bridge matrix.

Yeah, I was ready to suggest you try another battery because I felt yours may not supply enough, but 330mA I wouldn't have thought eighter. At least you've learned some things...

L298N is a little beefier dual H-bridge, you can parallel the h-bridges to get more current.

Yea, wow, it got repetive DC output of 2A per channel, not bad at all. Thx for poiting it out.

After I connected reversed 5V polarity in to sharp IR range finder it gives random values or simply - it doesnt react to distance. Can such device die so easely? I mean 5V reversed polarity isnt much. 

Most active electronic components die after applied reversed polarity... Unfortunatelly...

Great :S Thx for info though

Good thing -  my rc car bot is working and I thank you all for your help. It even got IR remote control now, how cool is that :P Bad thing though - my power supply only gives 1A current and the car cant rotate. Therefore  I decided to buy a good 4,5Ah NiMh accumulator. But I dont know what charger to buy. The cheapest one is 10$ and looks like this:

And has following properties:

Charge current/ Charge time pro 100 mAh for 7.2V

180mA / 45 min

I did the math: 4,5/0,1*45 = 2025 minutes. 2025 / 60 = 33.75h. Okeeey, 33h charge time? Really?

Another cheapest charger comes for 50+$ and is a digital thingy with nice features, but is kinda expensive:

This one has 0,6A charge current, which should charge my 4,5Ah battery in 10h. It also got car terminal and many nice features such as overcharge protection, bad cells detection etc. Both cant LiPo though.

There is a third one for the same 50$:


What is nice about that charger is that it can charge from 0.3A up to 3A. I mean what, can you really charge a 3Ah battery in just an hour? it can also do LiPo but only up to 3,7V ones. It also has same overcharge protection which is really cool. What I dont understand is that here: http://www.rcmarket.org/Power-Peak-A4-EQ-LCD-230V-12V.html it says the output voltage is 16V. Can I charge 7,2V accu with that? It also says: 

Charge current with cell count (12 V operation): 

2S = 3 A 

3S = 3 - 2.4 A 

4S = 2.2 - 1.8 A 

So 1S is one cell or how? My 4,5Ah battery is 6 cells. And I guess no 3A charging for that :/


So what charger would you recommend? I would go with the last one, if it can really do 3A charging. Also what is your experience with chargers? Should I invest 50+$ for a really nice charger? Be cause 33h charge time is simply unacceptable, if I did the math right.


  • It can charge 4-8 NiMH cells. It can also charge 1-4 LiPO cells. In the second picture in the link you provided it shows an 11.1V lipo charging:

  • Yes, an NiMH 3000maH battery will charge in around an hour at 3A.
  • The "S" ratings apply to the Lipos, not the NiMHs. It is short for "series" ie 1S = 1 x 3.7V cell, 2S = 2 x, etc. "P" stands for "parallel" if you ever run across it.
  • The amount of current used to charge with (and hence the charge time) is only manually adjustable for NiMH batteries on that charger. LiPOs are done with an automatic CC-CV setup using 0.3A to 3A.

Also, between those chargers, I'd get the last one. It has flexibility between battery chemistries, and as you noted, the first one will take fooooooorehhhhhhvah.