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[Reply #30 on:]

The resistors go the other way round (470 ohm to the lower transistor, 100 ohm to the upper transistor), and both the 1.5V and the 3.5V need to be increased to 5V if you want to feed about 3.5V to the motor.

[Reply #31 on:]

Yes but swap the resistors around, and provide 5volts (not 1.5v) to the base and 6-9volts(not 3.5v) to the actual power source.

Edit: dc42 beat me to it.

[Reply #32 on:]

The resistors go the other way round (470 ohm to the lower transistor, 100 ohm to the upper transistor), and both the 1.5V and the 3.5V need to be increased to 5V if you want to feed about 3.5V to the motor.

thanks for the help, but my problem is in the robots motor. it only has lower than 4v i think for its dc motor, and i want to amplify it to a bigger volts. and replacing its motor to a bigger motor,. 6v motor.

pls help me. read my past post for more info. thanks.

[Reply #33 on:]

Can you show us a picture? What is this motor in, does it have its own housing, holding it in place. You might not be able to change it.

Post a picture, that way we will have a better understanding of what your trying to do.

[Reply #34 on:]

Can you show us a picture? What is this motor in, does it have its own housing, holding it in place. You might not be able to change it.

Post a picture, that way we will have a better understanding of what your trying to do.

i want to amplify the volts produced by the line follower to power its dc motor, since its to weak to carry my sla 7v battery so i will modify my dc motor to a bigger and stronger one,. the logic of hbridge is correct but the hbridge wont work at all.






the power source of the robot is also from the sla battery.

[Reply #35 on:]

Those motors are going to require a lot of current, your best bet now would be to get a actually Hbridge board. http://item.mobileweb.ebay.com/viewitem?itemId=251080674810&index=1&nav=SEARCH&nid=83702557639

[Reply #36 on:]

Those motors are going to require a lot of current, your best bet now would be to get a actually Hbridge board. http://item.mobileweb.ebay.com/viewitem?itemId=251080674810&index=1&nav=SEARCH&nid=83702557639

you know i cant, because im in the philippines, im in the part of the philippines where those items are not available.

i would travel far away to the capital manila to get those items.

is their any one that can help me using only basic transistors?

i think i will not found the answer any more. for ever. i am loosing my hope now

[Reply #37 on:]

Can you get hold of DPDT relays (or SPDT relays)?
Use those instead of the H-bridge.
I think I've already suggested this.

[Reply #38 on:]

its to weak to carry my sla 7v battery

Hardly surprising - that battery is absurdly oversize for a 'bot that small. How many months were you hoping this thing would run between recharges?

[Reply #39 on:]

How many transistors did you get, maybe you can double them up and make them into darlington pairs.

http://www.google.com/imgres?hl=en&safe=off&sa=X&tbo=d&biw=1440&bih=754&tbm=isch&tbnid=JwhGtXRza51_UM:&imgrefurl=http://www.opencircuits.com/Basic_Circuits_and_Circuit_Building_Blocks&docid=ByS_Bn7_5pUhSM&imgurl=http://www.opencircuits.com/images/3/30/Dtrans.png&w=500&h=356&ei=SR0JUc7iLua20AGKy4CwBw&zoom=1&iact=rc&dur=4665&sig=106574055291386674452&page=1&tbnh=178&tbnw=266&start=0&ndsp=19&ved=1t:429,r:2,s:0&tx=121&ty=88

[Reply #40 on:]

How many transistors did you get, maybe you can double them up and make them into darlington pairs.

http://www.google.com/imgres?hl=en&safe=off&sa=X&tbo=d&biw=1440&bih=754&tbm=isch&tbnid=JwhGtXRza51_UM:&imgrefurl=http://www.opencircuits.com/Basic_Circuits_and_Circuit_Building_Blocks&docid=ByS_Bn7_5pUhSM&imgurl=http://www.opencircuits.com/images/3/30/Dtrans.png&w=500&h=356&ei=SR0JUc7iLua20AGKy4CwBw&zoom=1&iact=rc&dur=4665&sig=106574055291386674452&page=1&tbnh=178&tbnw=266&start=0&ndsp=19&ved=1t:429,r:2,s:0&tx=121&ty=88

what is the difference between the normal transisotr switch and a darlington connection?

[Reply #41 on:]

what is the difference between the normal transisotr switch and a darlington connection?

Much higher gain

[Reply #42 on:]

Can you get hold of DPDT relays (or SPDT relays)?
Use those instead of the H-bridge.
I think I've already suggested this.

i searched it in google, the dpdt relay.
i think that is not possible. the dc motor continues to turn in a direction if there is no voltage in the relay...

[Reply #43 on:]

what is the difference between the normal transisotr switch and a darlington connection?

Much higher gain

thanks for the fast reply.

the darlington has no resistor in the base?

[Reply #44 on:]

Can you get hold of DPDT relays (or SPDT relays)?
Use those instead of the H-bridge.
I think I've already suggested this.

i searched it in google, the dpdt relay.
i think that is not possible. the dc motor continues to turn in a direction if there is no voltage in the relay...

 You need to use two relays, one DPDT to determine forward/reverse and a one SPST to to perform the stop/go command, this second relay's contacts is simply wired in series with the positive voltage coming from the motor battery.

Lefty