Imagine controlling a robot with your personal mobile phone. You find excitement in making such thing with basic concepts of electronics....
No need of programming, no microcontrollers....
Lets start!
Now I will explain the theory how to make this amazing toy.
The main part of this project is getting the signal from the mobile phone and accomplishing the task. This is done by a IC named 8870. Then how this IC takes signal from the mobile, to know this you must know about DTMF TECHNOLOGY...
DTMF means dual tone multi frequency. When you press a key on your mobile keypad each key corresponds to two types of frequencies as shown below. The two frequencies overlaps and they are transmitted. Then our task is to decode these frequencies and use them for controlling a bot. As said above this is done by the IC 8870. This ic decodes the dtmf signals and converts into BCD format.
For example if you press the key number 9 the ic gives the output as 1001.
To know more about dtmf, please refer to the below links or not just skip it.
1.en.m.wikipedia.org/wiki/Dual-tone_multi-frequency_signaling
2. www.siongboon.com/projects/2005-07-18_dtmf_circuits/
Now we will make a robot which can be controlled through a cell phone. For that I have choosen the following numbers.
2-forward
4-left
6-right
8-backward
Not only the above numbers you can use any number of your choice.
The components are given below
1.ic-8870 (dtmf decoder)
2.ic-74154 (4:16 decoder)
3.ic-7404 (Not gate-hex inverter)
4.ic-7432 (or gates ic)
5.ic-L293 (motor driver)
6.crystal-3.5795Mhz
7.resistors:
*100k-2
*330-1
*220-4
*330-1
8.capacitors:
*0.1uf-1
*0.47uf-1
9.Pair of dc motors (specifications as you like)
10.LED for indication
11.3.5mm male jack (not needed if bluetooth headset is used)
12.wire connectors
13.little electronics knowledge and patience
The circuit presented below comprises of above components and is explained below.
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| This circuit is taken from achu wilson blog as per your requests. i will upload my own circuit after few days. |
We can see that the input from the mobile is connected with a capacitor and a resistor to pin # 2. The dtmf decoder ic decodes the input signal and gives BCD output. The BCD output is given to the 4:16 decoder ic(74154). This ic converts the BCD into hexadecimal at pin #11 to #14 .
Now half of the circuit is completed. But here it must be noted that the outputs of the ic74154 is high. That means when the key 9 is pressed the output pins of this ic will be high except the output pin corresponding to 9 (it will be low). For this we have used NOT gates. Here we used the HEX INVERTER IC 7404. It is a ic consists of 6 NOT gates described in other post. If you want search my blog for gates.
Now the four outputs from the not gates is connected to the or gate ic( 7432) before connecting to a motor driver(l293d). This ic is a 2 input OR gates with four in number. The outputs from the four or gates is connected to the four inputs of the motor driver IC. This circuit forms the logic to drive our rover in required direction.
It is a dual h bridge ic that can drive two motors at a time. the maximum current it is designed to handle is 600ma per channel. If it exceeds this there is a internal circuitry to stops the flow of current thereby protecting the ic from over current. The maximum non repeatable current through it can withstand is 1A. The load voltage can be up to 36V which is applied at the pin no.8.
To drive the motor in forward direction we have to apply the logic as shown below to the corresponding pins.
Basing on how you want to control your rover using differential drive there is a arrangement in the circuit to change the mode of steering. Turning a rover involves one wheel to rotate and other to stop such that it turns right or left. Other way is to rotate one wheel in clockwise direction and other in anti clockwise direction to turn left or right. this second gives a sharp turning. Both the modes can be implemented in this circuit by just changing the jumper pins provided in the pcb.
Is the load current is more than 600ma then you can use ic L298. It can give maximum upto 1A per channel. But the drawback is that there are no free wheeling diodes in l298 ic. so you have to place fast switching diodes.
BLUETOOTH:
You may wonder that how it is possible to interface a bluetooth without using a micro controller. Here we will use a bluetooth headset. just open it carefully and desolder the speaker wires and solder new wires as shown. Be careful when soldering as it may damage the bluetooth module. Now carefully put the cover and seal it such that there are no loose connections. If you connect the bluetooth to cell phone and press the keys the DTMF signal is sent wireless the the circuit.
UNDER PROCESS
