So I made a program that send a square wave signal of 5V through the pin 7 & 6 (I put a screenshot of my program), and it's work when I observe it on an oscilloscope however when I connect it to the transistor my signal is only 1V so the H bridge doesn't work (I rougly have 0.3 V at the level of the coil). What should I do ?
First, it's about attention to detail. Have a good look online of various darlington pair h-bridge circuits, and notice that the left-side of the circuit will have an npn darlington pair and a pnp darlington pair. That is...two different types of transistors on the left-hand side. The same case will apply to the right-hand-side of the circuit.
Now take a look at the circuit that you showed...... and look at the left-hand side. Does that look like two different types of transistors? Or does it look like the same type?
I search on internet and they are H bridge composed with 4 npn transistors, I don't understand why it can't works ?
However you're right I'm wrong with my schematics, I reverse the polarity of the transistor on the right side but I don't do it on my real electric circuit I check.
If you do use NPN for the high-side drivers then they don't need base resistors, that will marginally increase the
output voltage. The low side drivers definitely require their base-resistors though.
Trying to use darlingtons for a 5V bridge is basically a fail, you lose maybe 1.5V at each end, leaving
very little left for the load.
You won't get 4V with darlingtons. If the current isn't too high simple BJT's will work (you'll also
need 4 freewheel diodes for them). BJTs in saturation will get to 0.2V perhaps, the high side one's
cannot saturate if NPN though, will need to be PNP (and need base resistors and will be inverted
drive).
With this circuit how much can I get ? Because actually think they are a problem, in my coil I have 0.5 V exactly like the tension of the arduino on the base pin of each transistor but I doesn't have load or less than 50mA.... It not works with little diodes...
Google "level shifting high-side switch Arduino" perhaps?
With this circuit how much can I get ? Because actually think they are a problem, in my coil I have 0.5 V exactly like the tension of the arduino on the base pin of each transistor but I doesn't have load or less than 50mA.... It not works with little diodes...
I really can't understand most of this paragraph I'm afraid. I've told you what darlingtons from a 5V supply
can do.
lucrus91:
With this circuit how much can I get ? Because actually think they are a problem, in my coil I have 0.5 V exactly like the tension of the arduino on the base pin of each transistor but I doesn't have load or less than 50mA.... It not works with little diodes...
By saying that, I would like to say that it is strange thats actually I have less than 0.5 V at the pin of the coil, no ? On internet some have around 3 V with this circuit.
Its not in the least bit strange as I explained above. Using darligtons as emitter followers for the high-side
switches loses you volts, using darlingtons at all loses you volts, everything about the circuit loses volts and
the load is very low resistance in the first place.