Boe-Bot Servos
I feel really dumb for posting this question, but whatever. I'm currently building a Boe-Bot and have made it to the section in the book where you hook up the servos and calibrate them. The issue I am having is the book shows how to hook the servos up to a Homework board, A board, B board, and C board. I have D board which the book doesn't mention. Now after looking at all the instructions it seems the C board is the closest to a D. It says to run the servos off either a 6v battery pack or a 7.5vdc 1000ma power supply. I have a 9volt battery currently hooked up and am wondering if the D board allows you to use a 9 volt in place of the 6v battery pack and the 7.5 volt power supply.
Comments
2) The main problem with using a 9V battery is that its current capacity is puny and servos can draw quite a lot of current when under mechanical load or stalled. There's also the issue of excess heat dissipation. With a 9V battery, the regulator on the BoeBot has to get rid of 4V at whatever current is being drawn. A servo can draw over 1A when stalled and several hundred mA when actively running under light load. Say the current draw is 250mA (1/4A). That's 4V x 0.25A = 1W of power to dissipate. The regulator will get quite hot. It'll probably be ok with that, but any higher current drain (like from 2 servos) will probably cause the regulator to shut down to save itself.
3) #2 talks about running the servos off the 5V regulated supply. You can set up to run the servos from the unregulated power input. DON'T! You can do that (and it's recommended) for use with a 6V or 7.2V battery pack, but 9V will damage the servos. The 9V batteries will not be able to put out the amount of current needed anyway. At 250mA, a 9V alkaline battery will be exhausted in about an hour and a half and it's output voltage will have fallen below 7V long before that.
Post Edited (Sharks) : 10/9/2009 9:58:01 PM GMT