New lower price for Axon II ($78) and Axon Mote ($58).
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[...] need to work out how to fit all the electronic components together with correct voltages etc.[...]Lithium Ion Battery Cell - 3.7V 2000mAh[...]Computer Fan specifications:Voltage, 12VVoltage Range, 6-13.8V
We also want to be able to control the speed of the fan via a knob.
We want the ability to set a timer, so would need a clock that the robot controller can grab the time from
Lastly, we want the battery to be rechargeable without disconnecting anything (e.g. a separate cable that we can plug into a charger without disconnecting battery from robot)
I know it's a big ask, but if you're after a little cash throw me a quote :-))
The fan although rated 12volts we are doing some testing as we don't want it to spin that quick, so a drop in voltage should be fine. I'll be testing that in the next week or so which will enable us to determine what we require better as far as voltage range to run the fan. It's difficult to explain but the fan is to create a small vacuum effect. I'm hoping that 3.7 volts will be enough to move it at the speed required. Otherwise we will look at 5v fans or higher rated batteries.
The Fan speed would be affected by voltage, so we basically need a knob that allows us to set the amount of voltage being received by the fan. It would only run when the unit is On (whether by setting the unit to On or when a Timer has activated). Thanks for the info on the controller!
I'll do our fan tests and get back to you with regards to that.
With regards to controllers I really don't understand how the voltage requirements work, for example the dual motor controller says:The motor supply voltage range is 4.5 to 13.5 V; the continuous current per channel is up to 1 A (3 A peak). The logic supply can be as low as 2.7 V, allowing operation with modern microcontrollers running at 3.3 V.The motors themselves will spin from 0.6v to 6V.However, if the battery is for example 3.7V then I could not supply 4.5V-13.5V controller for the motor supply voltage (even though the motor will run fine on 3.7V). So I'm confused as to why the motor supply voltage range on the controller has a minimum? (noting that the website says the controller and gearmotor are a great match)
This is a slow moving vehicle so lower voltage will be fine. Longest possible battery life is important as is the smallest size (therefore the choice of battery Li-Ion seems like the best option - if you have another suggestion for a 5v battery that is similar size and would have a similar life that would probably be ideal).
Motor Controller: http://www.pololu.com/catalog/product/1110
Robot Controller: http://www.pololu.com/catalog/product/1220 (min 5v)
Step Up/Down: http://www.pololu.com/catalog/product/2120 (2v - 12v input and output)
[...] should I be looking at: [snip] - my max length for the battery is 68mm so this will fit.
I haven't bought the components yet, want to get it straight in my head first :-))
Components List:Baby Orangutan Robot Controller: http://www.pololu.com/catalog/product/1220 (min 5v)Battery (As above)Gearmotors x 2: http://www.pololu.com/catalog/product/1122 (0.6v - 6v)MMA7361L 3-Axis Accelerometer ±1.5/6g: http://www.pololu.com/catalog/product/1251 (2.2-16 V)QTR-1RC Reflectance Sensor: http://www.pololu.com/catalog/product/959 (5.0V)Small PCB board
So my questions are:1. Given the Baby Orangutan can control two DC motors, and I have two gearmotors, where does that leave me with the fan? What would I need to control that via PWM, and how to attach a knob to control the fan speed?
2. Do I need a step up/down regulator if I'm connecting the DC motors directly to the Baby Orangutan and everything will run at 5V?
3. What do I need to charge the battery on board?
4. What else do I need (apart from a fair bit more knowledge :-)))?
I'll be getting a new soldering iron before I start this (my old one is not looking in great shape!), and have a multimeter.
I actually bought the Venom battery yesterday, as long as it will suit I'm happy. It's a small size for 1300mAh at 7.4v which was my main requirement :-)
Looking forward to getting all the bits and pieces. In the mean time, as funny as it sounds, my son has one of the large snap circuits kits so going to do a bit of a hands on refresher with that first for both of us!!
Problem 1: My initial problem is that the power on/off button on the switch simply doesn't work. I've resoldered it a few times and for some reason pressing the button does absolutely nothing, the unit always stays on. I've tried everything I can think of.
Problem 2: I really don't know how to proceed as far as voltage/resisters etc. to connect the following components: -A: Reflectance Sensor (http://www.pololu.com/catalog/product/959). I intend to use this to detect if the robot has moved under something.
B: Accelerometer (http://www.pololu.com/catalog/product/1251). I intend to use this to determine if the robot is moving and in which direction.
C: The 12 volt fan. At the moment I don't have a step up voltage regulator but intend to purchase this if suitable (http://www.pololu.com/catalog/product/2120). The fan needs to be able to be turned on and off by the Baby Orangutan controller. At this stage lets not worry about making it adjustable. Like to get as close to 12V to it as possible.
I used a transistor to turn on/off the fan which works brilliantly and was far easier than I'd imagined.
The only things I'm not really sure about are:1. How to get feedback to the IC with regards to battery voltage. Using either of the components you suggested [...]
I don't see a way to read back the value to the IC. Ideally I want the robot to detect it's low, say under 6.5V, then I'll swap green headlights for red ones, then if it drops to 5.5V or below to switch off.
2. How to charge the battery. The Lipo has a power output (2 pin) and balancing output (3 pin). To charge can I just splice the power output? Or should I splice both allowing the charger to use the balancer as well? Or is there a better way of doing it?
Why do I need resistors for the transistor?[...]The emitter voltage (output) is 5V as specified
The base voltage is the a switch which gets 5V at very low current when turned on.
From this I don't see a requirement to drop the input voltage using a resistor? Or am I missing something entirely?
The base current is 20mA (the output from the Baby Orangutan digital IO pins)
I can't seem to find an output value for it for the base current at all in the documentation.
So the fan actually drawns 0.1A, mind you I'm going to be putting a boost regulator (http://www.pololu.com/catalog/product/799) between the transistor and the fan, as the fan is 12V 0.1A.
1. How did you reach 0.6V with the emitter grounded?
2. When you say the fan is connected between the +5V PS and the collector, what do you mean? The fan is currently connected to the emitter and back to the main ground?
my brain is starting to hurt a little bit..haha,