Author Topic: H-Bridge design  (Read 3717 times)

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Offline anshulsanamTopic starter

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H-Bridge design
« on: November 26, 2013, 10:04:56 pm »
Hello everyone I realized after burning through 6 L293D's that they were getting old. I hated them mostly due to the fact that they were fragile. I also burned 3 of them because of static electricity. So I decided to try and make a cheap H-Bridge from transistors. This is just a test circuit what I need to know is: is the circuit correct, can this type of H-Bridge handle more than 2 Amps depending on the transistors used, and do you guys have any suggested modifications if it is wrong.
 

Offline Psi

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Re: H-Bridge design
« Reply #1 on: November 26, 2013, 10:32:28 pm »
You need resistors on the base, they cant be connected together like that.
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Offline w2aew

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Re: H-Bridge design
« Reply #2 on: November 27, 2013, 12:15:44 am »
In addition to the required base current limiting resistors, the two transistors on the right side aren't correct (collectors should be tied together, not the emitters).
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Offline c4757p

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Re: H-Bridge design
« Reply #3 on: November 27, 2013, 12:28:11 am »
I hated them mostly due to the fact that they were fragile. I also burned 3 of them because of static electricity.

Your schematic suggests you burned them for a different reason. >:D ;)
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Offline anshulsanamTopic starter

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Re: H-Bridge design
« Reply #4 on: November 27, 2013, 04:19:23 am »
I am sorry I have made another version here.
 

Offline Zero999

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Re: H-Bridge design
« Reply #5 on: November 27, 2013, 11:10:19 pm »
I am sorry I have made another version here.
As soon as T3 is turned on, all the transistors will burn.

Perhaps you destroyed your L293Ds by using them incorrectly?

 

Offline Psi

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Re: H-Bridge design
« Reply #6 on: November 28, 2013, 12:00:19 am »
You forgot the base resistors again.
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Offline calexanian

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Re: H-Bridge design
« Reply #7 on: November 28, 2013, 03:36:20 am »
A couple things. Your input 1 should be common (With current limiting resistors as mentioned) to Q1 and what i believe is listed as T3 and conversely input 2 to Q3 and T1. Additionally this will only work if the driving voltage of the inputs are up with the total load voltage source. Otherwise you would need a driving transistor on the inputs to handle that. Additionally the transistors you have picked there are kinda whimpy. I would look at like TIP122 and TIP127 darlingtons for ease of driving, current cap, etc etc.. Just my thoughts. I use that kind of affair for driving single coil latching solenoids and relays.
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Offline codeboy2k

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Re: H-Bridge design
« Reply #8 on: November 28, 2013, 08:27:00 am »
what are you doing?

"is the circuit correct, can this type of H-Bridge handle more than 2 Amps depending on the transistors used, and do you guys have any suggested modifications if it is wrong"

because you seem like you don't know what you are doing, even the basics of Ohms law, circuit analysis, and power dissipation, which you should try to know before you design a circuit.

It's like me putting gunpowder into a toilet paper tube, rolling up the end into a cone shape and asking a NASA rocket engineer if it will fly, and what should I do to make it fly (just in case I was wrong in my rocket design and it won't actually fly.)


 


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