transistor switch logic . very hard to solve this scenario.

dc42:
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.

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.

HazardsMind:
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.

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

HazardsMind:
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 =(

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

jaylisto:
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?

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

HazardsMind:
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?

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

Much higher gain

AWOL:
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...

AWOL:

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?

jaylisto:

AWOL:
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

the darlington has no resistor in the base?

Nope, just follow the link I gave you, to wire it.

HazardsMind:
the darlington has no resistor in the base?

Nope, just follow the link I gave you, to wire it.

i will try this thing.

i will also try the relay style of the others suggested solution

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.

Or, if you want speed control and have an appropriate transistor, you use that in place of the single-pole relay, and just use the DPDT for reverse.

AWOL:

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.

Or, if you want speed control and have an appropriate transistor, you use that in place of the single-pole relay, and just use the DPDT for reverse.

o! my friend will travel to manila, i will give her a favor to buy what i need.

some one say here that their is an hbrige built in an i.c? what exactly the name of the ic?

that has the capability of giving what i want. pls suggest what is that hbridge ic. to be sure do not suggest rare ones. thank you so much. im looking forward for your reply.

The two most common are SN754410 and L293D

HazardsMind:
The two most common are SN754410 and L293D

what is the difference between the two?

i search it and sn754410 looks like it only uses 1 motor.

and l293d can handle 2 motors.

so what do you prefer? note: i only have 3v for trigger, and 7v for the higher voltage.

The SN754410 can handle two motors @ 1Amp, the L293d I think can handle 2-3 Amps.