Greetings Everyone,
I am building a small robot and was wondering if the Baby’s VCC could support the following devices:
4 x Sharp GP2Y0D810 (5 mA x 4 = 20 mA)
2 x Wheel Encoders (14 mA x 2 = 28 mA)
1 x Parallax PING))) (30 mA)
Do you think this will work or am I too close to the 100mA limit?
I was also thinking of adding a 330uF cap to help with the surges.
BTW, I LOVE the new track set!
Thanks,
Brian
Hello.
The current you can get out of the regulator will depend on your input voltage (and the ambient temperature). The maximum power dissipation for the regulator is given by:
P(max) = (125°C - Tambient) / 220°C/W = I * (VIN - 5 V)
where I is the total current through the regulator, including what is being used by the electronics on the Baby Orangutan itself. I think you should be able to get close to the full 100 mA from the regulator for input voltages up to around 8 or 9 V, and note that the regulator can tolerate short-duration peak currents of up to 300 mA (typical).
I agree that adding extra capacitance is a good idea, especially since the Sharp and Ping))) sensors draw current in relatively large bursts. A single large capacitor across VCC and ground near the Baby Orangutan could be sufficient, but you might find it more effective to put smaller (e.g. 10 uF) bypass caps near each of your Sharp sensors and your Ping))) sensor. If you start getting glitchy readings from your Sharp sensors, I suggest you try this latter approach.
Oh, and I’m very happy to hear that you like our new track set. Have you built anything cool with it yet or that going to be the propulsion system for the robot you have under construction now? I’d love to see pictures of your tracked chassis if you have any!
- Ben
Thanks, Ben. I’ll give you suggestions a try. I am still trying to figure out the best choice for a power source. I am currently torn between a NiCad 7.2v, 6 x NiMH AAA’s or 2 x RCR123’s (3.0v). I like the RCR123’s because of their compact design but I am afraid that they may not allow enough current. It is a bit challenging trying to maintain the weight to power ratio, all while trying to keep things as compact as possible.
And yes, I am using the tracks. They seem to work very well during initial testing. However, I quickly discovered that keeping the center of gravity low is critical. I am using the 22T set and it can flip very easily. This is another reason why I want to keep the batteries small and light.
Thanks again for your assistance. This is my first robot and it has been a lot of fun. I’ll try and get pictures as I go along.
- Brian
