No worries. I hope you all have some fun, and get it working.
You can use those pins for sure, or the others. Pin 9 is an input and 8 is the corresponding output. Likewise, pin 11 is the input and 10 is the output.
As for the other pins, 13 is input and 12 is output. Pin 5 is input and 6 is output.
Max voltage for the 74HC14 is 7 volts, 6 volts to be safe. If that’s no good, there is a cmos chip that handles a higher voltage, the 74C14, I think, but don’t quote me. You want the schmitt trigger inputs for snappy changes from the output to the input of the h-bridge.
For the two inverters you don’t use, please tie the inputs to ground. I mean like the negative battery line. If you’re using pins 9/8 and 11/10, then tie pins 13 and 5 to ground.
Anyway, have some fun, check out some stuff on the web. It’s 10.30 here in Melbourne; past this old guy’s bedtime. G’night!
EDIT: Actually, you could probably about halve the value of R1, depending on the voltage you’re running at. If you’re running at 6volts you could go under 200 ohms for R1 with no probs. 330 is probably too high. Maybe try about 180 ohms first.
ok thanks again…last ok thanks again…last question. im getting a problem with choosing a phototransistor can i use this bpw77nb it has 3 pins im confused… (o.0)
There is a problem with the latest design change. You will need the 74HC14 after all.
I did a quick breadboard and, while the sensor portion works fine, the I Meg resistor on the input of the L293D causes problems.
The voltage at the L293D input will not rise above approx 1.8V. Using a 10k pullup is fine, but that does not give a sufficient delay. The input needs to be buffered from the effect of the 1meg resistor, so it’s back to the earlier design with the 74HC14 in the mix acting as a buffer between the delay components (1 meg/ 2.2uF) and the input of the L293D.
its working on the i used the first design and its working on the breadboad. but its really hard to adjust the potentios. and the motor output its kinda low i think its because of the transistors?? i used 2x 2n3904 and 2x 2n3906 and 1k ohms every base pins on the H-BRIDGE… but its a progress to our project thanks…
So, you’re using a 4 transistor h-bridge, with the 3906’s in the upper half, and the 3904’s at the bottom? How much current do the motors in the Tamiya unit want?
1k on the bases should be fine. What voltage are you running the whole set-up at?
Double check you’re using the correct transistor pin-out.
You might need gruntier transistors, If you have any DPDT relays, that could be an option, too.
Remember to sheild the phototransistor from ambient light.
its all working now…im its all working now…im using 4AA batteries. the motor i used is only a generic DC motor from the twin gearbox of tamiya… but the two outputs does not sync in speed… and it is too slow… i think it cant support the mobot. but well see…
The motors appear to be low voltage (3 - 6 volts) but draw a fair whack of current, certainly more than the 3904/3906 can handle. Check the specs in the Mabuchi motors pdf, referenced on the same page.
I think you’ll need to beef up the transistors in your h-bridge.
You could also look at swapping out the high current motors in the gearbox with something like this:
Used to be able to buy a similar motor called a P9000. Maybe check your local electronics suppliers for motor with specs approximately that of the pololu motor.
