I had a couple of CD/DVD writer scrap. When I opened them I found the Lasers are in working condition and the Motors looks the same. Then I came across the Laser Engraver for custom laser works from these scrap Lasers. I found many people had done and driven these Bi-polar Stepper Motors by the use of Micro controllers. many people found it easy. Then lets make it from scrap by adding all general purpose , easily available components. This is just the Simulation Model but will make the physical one shortly.
The Part List:--
1 C1 10uf/16V polarised
1 C2 500n ceramic
1 C3 100n ceramic
8 D1-D8 1N4007 or 1N4001
2 D9-D10 1N914 or 4128 (High speed switch)
4 Q1-Q2,Q5-Q6 2N3906
4 Q3-Q4,Q7-Q8 2N3904
8 R1-R8 1.5K 1/4 watt
2 R9-R10 4.7K 1/4 watt
2 R11-R12 50K 1/4 watt
1 RV2 100k Trimpot
1 SW2 SW-SPST
1 U1 74LS109 TTL
1 U2 74LS86 TTL
1 U3 NE555
1 U5 74LS05 TTL
Step 1: Flip Flop Logic and H-Bridge
The Flip Flop We are using is a Dual J-K Flip Flop 74LS109 .
Apart from it we need a 74LS86 Quad EXCLUSIVE-OR Gate and a HEX Inverter SN54/74LS05.
These 3 Component will make the necessery logic for full rotation of the motor.
~~~~ The H-Bridge~~~~~~
Honestly we can use a straight forward H-Bridge IC preferably L293D.
but we don't actually need such high current ratting IC. We just made it with 2N3904 and 2N3906 with 1N4007 and 1.5K resistors.
However the Transistors can be of high current and frequency ratting if the motor demands so.
Step 2: The Clock Pulse Generator
We may all came across the Great IC 555 multivibrator.
Yes this is the heart of the clock pulse generator. Seriously this is the Heart of the Circuit also since this will control the Speed of the motor.
This circuit will generate square wave of duty cycle 50% from 1 Hz-100 Hz depending on the Value of C3.
How ever I found the value to be 500 nf for our requirement.
Step 3: Final Assembly (All in One)
This diagram shows the combination of all the sub-circuits. The circuit on simulation worked like charm and took 4 Days to tune to best.
Please note the motor may be 12V or 5V depending upon type. However a separate supply is advisable since Inductive load will produce ripple and harmonics in the control DC supply.
All flip flops and inverter are TTL so the circuit will need 5V as supply.
We can add 5 Nos 100nf Capacitors ((Code 104)) to attain 500 nf capacitance.
The switch SW2 is forward - reverse Switch.
Any ways its virtually done and will be done Physically shortly.
Thanks and Happy Electronics.........................