Continue to Site

Welcome to our site!

Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Power supply drops down

Status
Not open for further replies.

shico90

New Member
Hello,
I'm having a very strange thing going on, when I connect my H bridge circuit to +9
power supply the voltage of the power supply drops to 5 v, I don't know what is the problem
that is the H bridge circuit
**broken link removed**
I connect the VDC to +9 v power supply and the 4 inputs to the H bridge connected to the MCU which is connected o another power supply 5 v
and the two power supply grounds are connected
I don't know what happens to the voltage, why is it dropping, I tried to separate the two grounds, but still there is the problem
Can anyone help?
 
The input signal level for the PNP transistors must be the same as their emitters (the supply voltage) or the PNP transistors will never turn off and the battery will be shorted.
But your input signal is only 5V from the MCU and if the battery is 9V then the signal should also be 9V.

You could add an NPN transistor to drive each PNP transistor to fix it.
 
I don't know how to thank you, thank you very much and sorry for my mistake
Is this circuit good to drive the PNP?
**broken link removed**
 
You need resistors in the base of each 2N2907 otherwise there will be very high current going through the bases of both bridge transistors that are on, which will likely blow at least one of the transistors.
 
My circuit uses power transistors and low value base resistors for 1A output. It has all the resistors that are missing on the circuit you found:
 

Attachments

  • 1A H-bridge.PNG
    1A H-bridge.PNG
    12.4 KB · Views: 154
Status
Not open for further replies.

Latest threads

New Articles From Microcontroller Tips

Back
Top