Homebuilt ROVs Forum

fluffy111 wrote:On i2c you can have as many slaves as you want connected to one master (Arduino in your case). That is because every i2c device has it unique serial number and while you are programming master there is a sequence when every device should present itself (one at the time) and master save it (in your case on EEPROM). Then every time you want data you send serial number on i2c bus and only one device will answer. It is very similar to 1wire (for i2c some say that is 2wire protocol).

Regards

that isn't exactly correct. i2c uses a 7-bit address space, which means that you can only have a maximum of 128 devices on a network. however, due to loading of the bus, that number is likely to be a lot lower. additionally the address space is divided into different categories (memory, sensors, etc.) and most devices only allows you to set the lower 1 to 3 address bits to a unique value, thus further reducing the number of identical devices allowed on the bus.

there are devices like i2c switches and muxes which help with this problem, but that introduces more complexity.

One thing that i was just thinking what do you do when the lipo alarm goes off?

A couple of options here I can think of. You can set the some lipo monitors at different levels. eg. you can set the cell voltage to alarm at say 3.3 volts and that would give you enough reserve to bring the rov back to the surface before you reached 3.0 volts. Or if worse comes to worse pull the sucker to the surface via your tether.

One option that i had considered is to have a cut-off relay on each pack so when the alarm goes off it cuts the power draw from that cell, and have a reserve battery to get to the surface.

Thats a BRILLIANT idea and should be easy enough to do with just a simple double pole double throw relay. Have the relay coil controled off the main battery monitor. When you alarm the relay status changes and the NO contacts close switching to your reserve battery.

Wouldn't you get a power surge as you switch from one battery to another?

electronicscrazy wrote:Wouldn't you get a power surge as you switch from one battery to another?

There will be a sudden increase of voltage but this doesnt do much harm as long as you have fairly ok designed power system. as a thumb-rule you should always have some sort of regulator between the High-amp equipment and the low-amp/power electronics. so if you would have a ESC + Arduino based system, i would have a DC/DC converter between the batteries and the powerinput of the arduino(even if it could handle the main voltage of the batteries)