Hi,
I made the circuit below and was wondering if its ok?
Seems to be OK (as long as we don't talk about the visual layout
)
Also do i need all the filtering capacitors?
The first one (left to right) is used as a buffer for the battery.
Next one is the input cap on the regulator - make it 220nF to 330nF.
On the output side you need a cap of 22..33µF.
The input and output caps are there to dampen noise and kill oscillations and the values I just mentioned is for regular regulators - they must be mounted as close as physical possibble to the regulator terminals.
With LDO regulators, you need to consult the datasheet for the exact regulator, as they vary a bit and eg. a too large output cap might actually make it oscillate as well.
The 100nF + 10µF is drawn in by someone that only learned enough to be dangerous and it stems from other instances, where you need to parallel several values to get the widest band of noise dampening.
Since the regulated voltage is just used for the motor, you might consider using 3 AA primary cells (or 4 NiMH AA cells) directly to the motor voltage terminal (and ground) and drop the regulator and the losses it introduces.
Also if the motor is a small 3V one should i reduce the voltage to it? The minimum from the H-bridge is 4.5V...
According to the datasheet, the SN754410 has got a typical drop of 2.1V at a 500mA draw (there's a drop on both high and low side), so you should get around 2.9V (at 0.5A).
If you want the motor to run slower, just use PWM (on pin 1 if you want to keep it simple).
You didn't mention your 9V source, but if it's a non-rechargeable PP3 battery (box shaped "transistor" battery), you have the explanation of it not working, as a PP3 simply haven'tgot the oomph for this.
Another thing is, that the voltage regulator needs to drop 3V, so anything below 8V will throw the regulator out of regulation. A 9V battery drops from ~9.6V when brand new, to 5.4V when completely exhausted and will only be usable for this during a short part of its life.