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### Topic: transistor switch logic . very hard to solve this scenario. (Read 11601 times)previous topic - next topic

#### dc42

#30
##### Jan 28, 2013, 02:29 pm
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.
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#### HazardsMind

#31
##### Jan 28, 2013, 02:30 pm
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.
My GitHub:
https://github.com/AndrewMascolo?tab=repositories

#### jaylisto

#32
##### Jan 29, 2013, 04:53 pm

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.

#### HazardsMind

#33
##### Jan 29, 2013, 05:09 pm
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.
My GitHub:
https://github.com/AndrewMascolo?tab=repositories

#### jaylisto

#34
##### Jan 30, 2013, 04:22 amLast Edit: Jan 30, 2013, 04:24 am by jaylisto Reason: 1

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.

#### HazardsMind

#35
##### Jan 30, 2013, 05:40 am
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
My GitHub:
https://github.com/AndrewMascolo?tab=repositories

#### jaylisto

#36
##### Jan 30, 2013, 08:57 am

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 =(

#### AWOL

#37
##### Jan 30, 2013, 09:00 am
Can you get hold of DPDT relays (or SPDT relays)?
Use those instead of the H-bridge.
I think I've already suggested this.
"Pete, it's a fool looks for logic in the chambers of the human heart." Ulysses Everett McGill.
Do not send technical questions via personal messaging - they will be ignored.
I speak for myself, not Arduino.

#### PeterH

#38
##### Jan 30, 2013, 02:01 pm

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?

#### HazardsMind

#39
##### Jan 30, 2013, 02:15 pmLast Edit: Jan 30, 2013, 02:18 pm by HazardsMind Reason: 1
My GitHub:
https://github.com/AndrewMascolo?tab=repositories

#### AWOL

#41
##### Jan 30, 2013, 04:03 pm
Quote
what is the difference between the normal transisotr switch and a darlington connection?

Much higher gain
"Pete, it's a fool looks for logic in the chambers of the human heart." Ulysses Everett McGill.
Do not send technical questions via personal messaging - they will be ignored.
I speak for myself, not Arduino.

#### jaylisto

#42
##### Jan 30, 2013, 04:06 pm

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...

#### jaylisto

#43
##### Jan 30, 2013, 04:08 pm

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

Much higher gain

the darlington has no resistor in the base?

#### retrolefty

#44
##### Jan 30, 2013, 04:10 pm

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

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