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### Topic: transistor switch logic . very hard to solve this scenario. (Read 8810 times)previous topic - next topic

#### jaylisto

##### Jan 21, 2013, 02:44 pmLast Edit: Jan 21, 2013, 02:45 pm by jaylisto Reason: 1
i dont know if im in the right category to post this one.

line follower with 3v power to its dc motor. line follower controlled by arduino.

i want to modify the smaller 3v dc motor to a bigger 6v dc motor by some kind of a reason., since the robot only produce 3v to power the small dc motor. i want to hook the 6v motor to another 6v power source and by using transistor as the 3v will switch the 6v dc motor.

the problem is. the robot can reverse the dc motor whenever its out of track with the line. reverse the +/- vice versa so that the motor can turn forward and reverse.

how can i apply the transistor switch if that is the case?.

if there is a solution, pls give me the diagram.
jaylisto

#### HazardsMind

#1
##### Jan 21, 2013, 04:17 pm
My GitHub:
https://github.com/AndrewMascolo?tab=repositories

#### PeterH

#2
##### Jan 21, 2013, 04:25 pm
It sounds as if you already have a solution working with the 3V motor. What circuit are you using to drive that? It may be that the existing circuit is already capable of handling the extra voltage and current.
I only provide help via the forum - please do not contact me for private consultancy.

#### jaylisto

#3
##### Jan 22, 2013, 02:43 pm

Or possibly a simple H bridge chip, http://www.elektroda.pl/rtvforum/files-rtvforum/ckt_mtr_1826.jpg

wow, you are so amazing, it seems you like helping people here...
what kind of transistor do i need? 3v drives the 6v power?...
i have 4 transistor npn tip 41 in my box... is tip 41 to much?
jaylisto

#### HazardsMind

#4
##### Jan 22, 2013, 03:10 pm
If your following the first link I gave you then, tip 41, should be fine. But looking at the data sheet, its made for high voltage applications. Kinda overkill for your project. You may just want to get some 2n3904 or 2n3906 NPN transistors from RadioShack, or simply a H-bridge DC Driver IC.
My GitHub:
https://github.com/AndrewMascolo?tab=repositories

#### dc42

#5
##### Jan 22, 2013, 03:27 pm
If your motor take less than 1A you can use this http://www.farnell.com/datasheets/39120.pdf. It comes in an SO-8 package, so you will need an SMD adapter board to use it unless you are designing your own PCB.

There are some low-cost H-bridges around based on the L293D and L298N bipolar H-bridge chips, but they have a voltage drop of around 2V. So you would need a power supply providing around 8V for your 6V motor if you use one of those.

Another solution is to use a single mosfet to control the motor on/off and speed, and a DPDT relay to reverse it.
Formal verification of safety-critical software, software development, and electronic design and prototyping. See http://www.eschertech.com. Please do not ask for unpaid help via PM, use the forum.

#### jaylisto

#6
##### Jan 22, 2013, 04:02 pm

If your motor take less than 1A you can use this http://www.farnell.com/datasheets/39120.pdf. It comes in an SO-8 package, so you will need an SMD adapter board to use it unless you are designing your own PCB.

There are some low-cost H-bridges around based on the L293D and L298N bipolar H-bridge chips, but they have a voltage drop of around 2V. So you would need a power supply providing around 8V for your 6V motor if you use one of those.

Another solution is to use a single mosfet to control the motor on/off and speed, and a DPDT relay to reverse it.

sorry, in my home there is no ic h-bridges i think.. even 555 is not available
jaylisto

#### jaylisto

#7
##### Jan 22, 2013, 04:09 pm

If your following the first link I gave you then, tip 41, should be fine. But looking at the data sheet, its made for high voltage applications. Kinda overkill for your project. You may just want to get some 2n3904 or 2n3906 NPN transistors from RadioShack, or simply a H-bridge DC Driver IC.

yes the 1st link . if i need to have the diode to protect the motor whats the code of the diode to be use in mine?. do i really need that diode or its ok without them?

i will take the information of 2n3904 and 2n3906. i hope this transistor is available to the nearest store located in small city from our home. but if 2n3904 is not common, im sure its not available. take note. can it hande the sla 7v 4 amphere battery?
jaylisto

#### AWOL

#8
##### Jan 22, 2013, 04:14 pm
Or, you could control the speed with a transistor, and handle the reverse with a DPDT relay.
"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.

#### HazardsMind

#9
##### Jan 22, 2013, 04:25 pm
No diode needed, but if you are having problems finding the parts, go with the other given alternative from dc42
My GitHub:
https://github.com/AndrewMascolo?tab=repositories

#### jaylisto

#10
##### Jan 22, 2013, 05:37 pm

No diode needed, but if you are having problems finding the parts, go with the other given alternative from dc42

what do you mean by dc42?
jaylisto

#### dc42

#11
##### Jan 22, 2013, 05:39 pm
Formal verification of safety-critical software, software development, and electronic design and prototyping. See http://www.eschertech.com. Please do not ask for unpaid help via PM, use the forum.

#### jaylisto

#12
##### Jan 22, 2013, 06:03 pm

ow sorry. as i sad, im sure its not available. but i will check the availability tomorrow.
jaylisto

#### dc42

#13
##### Jan 22, 2013, 07:19 pm
If you update your profile with the country you live in, then we might be able to suggest suppliers.
Formal verification of safety-critical software, software development, and electronic design and prototyping. See http://www.eschertech.com. Please do not ask for unpaid help via PM, use the forum.

#### jaylisto

#14
##### Jan 23, 2013, 02:01 amLast Edit: Jan 23, 2013, 03:07 am by jaylisto Reason: 1

If you update your profile with the country you live in, then we might be able to suggest suppliers.

i updated my profile as you say. no suppliers here. its Philippines.
jaylisto

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