My basic suggestion to you, if you don't mind me butting in here,·is to proceed as follows. DON'T rely on what you THINK you may know, but ask simple straight-forward questions in lieu of the silly run-on messages which do not help you or us.
Let's try this for starters regarding your currrent question
-
YOU: I have a feeling that I can use an H-Bridge for my application, but how can I use an H-Bridge to control TWO DC PM motors?
US: H-Bridges come in single- and dual- formats. What you want is a DUAL H-Bridge. There are numerous single chips available to provide that facility. Here·is one·of them (attached) - see if·it meets or exceeds·your needs.
Please don't think I'm being harsh with you, I'm only trying to help you to help yourself better. Nearly 40 years of providing technical assistance have taught me that sometimes newer folks are really looking for better direction, and don't know how exactly how to ask for it. If that's not you, I humbly apologize.
i completley understand thank you bruce, im not real sure on the dc motors amprage either... considering i did not buy them... i know that they asre running off of a 7.2 volt 1800MaH Lithium rechargable battery. how can i find the current of things, ive noticed its very important and when i dont buy the object i do not know the current. also is there somthing a little more simple for the control of two motors? these 24 pin dips and stuff is a little overkill for a project im just using to keep me busy lol
What you need to do is use a multi-meter with an appropriate scale and capacity to check (at least) the running current of the motors. You do this by placing the meter in SERIES (in line) with the POWER LEAD (+ lead) of the motor, and then turn the motor on.
+ power -> (+) lead of meter (METER) -> (-) lead of meter -> + lead of motor -> (MOTOR)
WARNING: If your meter does not have AT LEAST a 2 amp current rating and scale, I'd borrow a meter that has such a capacity. FAILURE to do so will BLOW THE METER unless is is internally fused apropriately. "Cheap" meters are often not fused appropriately
i tried doing the transistor hbridge but it only put out 2 volts? any explanation? i think im not putting the transistor in or maybe im supposed to hook the mosfet to it? hopefully you can make sense of it...
i have successfully ran the small motor very faintly due to the wrong transistors fairly easily, tomarrow im heading to radio shack to buy all my parts! hopefully i can figure this out... im definantly going to need a breadboard add on...
alright ive tried and tried and my transistors are getting hot and i keep unplugging all power so can someone tell me which what these go... meaning CBE thanks guys
You may wish to start from scratch one transistor at a time to get each one to work on a breadboard till you understand each one, then tackle the entire thing.
You should think of each transistor as nothing more than a switch with an input(base) that turns the switch "on" to allow current to flow from collector to emitter.
On the little plastc guys. the "input switch or base" will go to the center pin 2. See the link
I think on the Tip's the base is always pin 1, c is 2 and e is 3 but check your part.
Read this link to get a better understanding and do tests with each transistor seperately to make sure you are hooking them up right. Also, test the ones that got hot to make sure they still work. The emitter is the pin with the arrows on the drawing. The base is always the "switch input".
If they are getting hot then either they are hooked up wrong or you are putting too much current to the motor. I dont think you really meant to have -6 and vss tied together, both those should just be vss. I doubt you really hooked up bopolar +- 6 supply did you? Double check connections once you get the pins right. With that low of voltage you shouldnt get much heat.
just do that circuit and lose the optos that are shown. you cant get any simpler than that using 4 mosfets. apart from that, you really need to digest the previous mentioned transistor info to understand how the transistor works, they are very simple. if you understood how simple, it would all make sense to you and you could visualize the ciruit in two seconds. forget that pnp/npn 8 transistor thing you posted earlier.
i understand them, correct me if im wrong but the depending on the base, the collector will take in voltage and allow it out the emmitter with a higher current, the base and the emmit run corrosponding to one another, if base is high, current out of emmit will be high
will...89,
Looking at your picture vs. your schematic...· Are your resistors represented in there anywhere?
Maybe you're going at this a bit hit-or-miss.
I've attached a pic that shows the lead outs of the transistors indicated in the schematic you U/L'ed.· Maybe it'll help you out some, looks like you need some help in that regard.
well sort of, if the base is high, the emitter will reflect what is at the collector, as it is only a switch that makes a connection. if 6v is at the collector, then 6 v will show up at the emitter, but if gnd is at the collector then you get my drift.
in an hbridge, you will notice that at the top of the schematic the +6 is getting switched on, but on the bottom of the schematic, gnd is getting switched. you should get a meter and play with some transistors to see the results first to get the picture. think of the tranny as an spst relay for now.
if you turn both stamp pins high at the same time, you will soon smell something funny if the room. always have your program turning off one pin before turning the other one on. preferably with at least a few milliseconds pause between the changes to avoid problems.
if you are using the mosfets the gate(same as base with the others) is pin 1 if you are facing the tranny with pins down. put +6 to pin 2(drain) and the motor at pin 3(source) for the high side of the schematic.
look at this link below i found it googling up irf510 hbridge it is the thrid item listed. if you spent 5 minutes on google you would save yourself a lot of headaches [noparse]:)[/noparse] no offense
see page 6 for irf510 hbridge in is most simplest form all you gotta do is find out what pin is gate, drain and source it should be as i stated or on the package: just ignore the pwm part at the bottom of the circuit, run yours to gnd as before.
alright i got it to power the small motor but for some reason im connecting a 7.2 volt device and its outputting 4 volts.... im guessing there is not enough current? there wasnt enough but i connected the ground from the battery to the vss and it ran.... thats using tip31 and tip42 both x2 so im guessing i do not have enough connected to run the currecnt from the 7 volt battery>?
drop the voltage if you are sending more than the motors are rated at.
you could pwm the transistors instead of keeping them high all the time, or write some code that when it is "on", it is really toggling on and off based on your pause length, similar to pwm:
but1 var in1
forward var out2
pausetime var nib
main:
pausetime = 10
if but1 = 1 then motorforward
go to main
motorforward:
do while but1 = 1
forward = 1
pause = pausetime
forward = 0
pause = pausetime
loop
goto main
adjust pausetime till it works but doesnt get too hot, you vould also set a pot with rc on a pin that could translate to pausetime and adjust it by hand to find a sweet spot, or just keep trying numbers.
if you have no sinks, get some small nuts and bolts and attach anything metal, tin foil whatever
it seems what when the motors are running they stay considerably cool, only when the motors are disconnected or not running is when they get very hot, i layed a heat sink across them because i only have one.... the metal backing doesnt connect to anything electrical does it? i thought pwm only sent high pulses? what about the lows.... and come to think of it the circuit will run regardles sof power to the microcontroller from the main battery power source so i dunno
Post Edited (willthiswork89) : 7/31/2006 6:30:23 AM GMT
Based on your original schematic, a very fundamental thing is being overlooked here with regards to using
bipolar transistors. Your supply voltages are different from each other causing the PNP transistors to never
completely turn off.
I can illustrate this in a way that might make more sense if you forget for a moment that the transistor has
a collector and look at it from just the B-E (Base-Emitter) junction. Keep in mind that the B-E junction of a
transistor "looks" like a diode at ALL times regardless of whether the transistor is ON or OFF. Also, remember
that a transistor is a current device, once you have reached the forward bias of the transistor, usually .6V to
.7V, the amount of current you supply to the transistor Base gets amplified across the C-E (Collector Emitter)
junction by the Hfe factor (or gain) of the transistor as long as the current across the C-E junction does not
exceed the transistor ratings.
Based on your schematic, consider the following with just looking at the PNP transistors and with the
exception that you are running the supply with 7.2V....
Q9 Q2
5V (I/O) >--------/\/\----|<----|<------< 7.2V
1K B E B E
1V .6V .6V
I = 1mA
Q9 Q2
0V (I/O) >--------/\/\----|<----|<------< 7.2V
1K B E B E
6V .6V .6V
I = 6mA
... assume that the resistor is 1K whether the I/O is set to HIGH (5V) or LOW(0V) there is still an
adequate voltage and current that keeps the PNP transistors "ON". (Q1 and Q7 also apply to this)
Suppose that the Hfe or gain of the transistor is 100, even when the I/O pin is HIGH you have 1mA
of current across the B-E junctions. With an Hfe of 100, the transistor is trying to drive 100mA when
it doesn't need to. This equals HEAT
The HEAT problem that you are also having with your mosfets can also be related to the issue of
having different supply voltages. In either case especially with mosfets, unless you are exercising
them in their linear region or if they are not correctly chosen, they should NOT be getting hot. Bi-polar
transistors will loose heat right off the bat because of the .6V drop across the C-E junction.
For Bipolar transistors:
Suppose your supply is 7.2V and you are trying to drive 500mA. Since you immediately loose .6V, you
end up wasting 300mW of HEAT across the transistor.
P = I * V
P = 500mA * .6V
P = 300mW
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔ Beau Schwabe
IC Layout Engineer
Parallax, Inc.
alright i will make up the thing and take a picture... i really appreciate everyone helping me out i feel like a retard, if i knew more about the motors i was driving it may help out.... let me get everything made up correctly and ill post pics
I'm not sure exactly what your point is here? The images are difficult to read.
The mention of the 'different' voltage supplies in my earlier post is in reference to the fact that the BS2 is running off of a 5V reference
while the H-Bridge is running off of a 7.2V reference. Not that there is anything wrong with this, it is done all the time, but the circuit
you are using for this is flawed.
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔ Beau Schwabe
IC Layout Engineer
Parallax, Inc.
what can i do to fix this, iknow that anyresistor, even my lowest 220 ohm resistor is too strong, if i put the resistor on the 7.2 supply the mototr will not run.... i tried to use the transistor hbridge but there is too much voltage loss.
You should be more specific and use proper terminology. I'm not sure what you mean exactly by the description you give of your lowest 220 ohm resistor being too strong.
Again, in your statement "...if I put the resistor on the 7.2 supply the motor will not run".
Yes, a transistor Hbridge does have a voltage drop of 1.2V and your motor will "see" 6V as it operates.
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔ Beau Schwabe
IC Layout Engineer
Parallax, Inc.
basically the motor will run when i connect battery to terminal. but if a take a 220 ohm resistor and place it in a bread board, place the positive terminal form the battery to the same row. and place the wire to the motor in that row. the motor will not run... what im getting at is that that little resistor and stopping the motor from running straight battery
Battery->220 Ohm Resistor->Motor Terminal #1
Battery(-)->Motor Terminal #2
this will not run due to a small current loss.
Im concluding that the motor is too large of a current draw to use the hbridge with the Transistors even with a darlington pair. i did although, get the motor to run from 4 IRF510 Mosfets with an extensive ammount of heat
Comments
My basic suggestion to you, if you don't mind me butting in here,·is to proceed as follows. DON'T rely on what you THINK you may know, but ask simple straight-forward questions in lieu of the silly run-on messages which do not help you or us.
Let's try this for starters regarding your currrent question
-
YOU: I have a feeling that I can use an H-Bridge for my application, but how can I use an H-Bridge to control TWO DC PM motors?
US: H-Bridges come in single- and dual- formats. What you want is a DUAL H-Bridge. There are numerous single chips available to provide that facility. Here·is one·of them (attached) - see if·it meets or exceeds·your needs.
Please don't think I'm being harsh with you, I'm only trying to help you to help yourself better. Nearly 40 years of providing technical assistance have taught me that sometimes newer folks are really looking for better direction, and don't know how exactly how to ask for it. If that's not you, I humbly apologize.
Regards,
Bruce Bates
What you need to do is use a multi-meter with an appropriate scale and capacity to check (at least) the running current of the motors. You do this by placing the meter in SERIES (in line) with the POWER LEAD (+ lead) of the motor, and then turn the motor on.
+ power -> (+) lead of meter (METER) -> (-) lead of meter -> + lead of motor -> (MOTOR)
WARNING: If your meter does not have AT LEAST a 2 amp current rating and scale, I'd borrow a meter that has such a capacity. FAILURE to do so will BLOW THE METER unless is is internally fused apropriately. "Cheap" meters are often not fused appropriately
Regards,
Bruce Bates
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
<!--StartFragment -->
http://www.blogcadre.com/blog/jason_striegel/howto_make_a_robot_car_-_part_1_overview_2005_10_25_13_22_21
i tried doing the transistor hbridge but it only put out 2 volts? any explanation? i think im not putting the transistor in or maybe im supposed to hook the mosfet to it? hopefully you can make sense of it...
You should think of each transistor as nothing more than a switch with an input(base) that turns the switch "on" to allow current to flow from collector to emitter.
On the little plastc guys. the "input switch or base" will go to the center pin 2. See the link
2n3906
http://www.onsemi.com/pub/Collateral/2N3906-D.PDF
2n3904
http://www.onsemi.com/pub/Collateral/2N3903-D.PDF
I think on the Tip's the base is always pin 1, c is 2 and e is 3 but check your part.
Read this link to get a better understanding and do tests with each transistor seperately to make sure you are hooking them up right. Also, test the ones that got hot to make sure they still work. The emitter is the pin with the arrows on the drawing. The base is always the "switch input".
http://www.kpsec.freeuk.com/trancirc.htm
If they are getting hot then either they are hooked up wrong or you are putting too much current to the motor. I dont think you really meant to have -6 and vss tied together, both those should just be vss. I doubt you really hooked up bopolar +- 6 supply did you? Double check connections once you get the pins right. With that low of voltage you shouldnt get much heat.
[noparse][[/noparse] If you go too far, you'll have to stay there.· [noparse]:)[/noparse] ]
looking at my schematic does it look hooked up right or is somthing not connected properly? also how can i use my IRF510 mosfets to make an hbridge?
just do that circuit and lose the optos that are shown. you cant get any simpler than that using 4 mosfets. apart from that, you really need to digest the previous mentioned transistor info to understand how the transistor works, they are very simple. if you understood how simple, it would all make sense to you and you could visualize the ciruit in two seconds. forget that pnp/npn 8 transistor thing you posted earlier.
Looking at your picture vs. your schematic...· Are your resistors represented in there anywhere?
Maybe you're going at this a bit hit-or-miss.
I've attached a pic that shows the lead outs of the transistors indicated in the schematic you U/L'ed.· Maybe it'll help you out some, looks like you need some help in that regard.
in an hbridge, you will notice that at the top of the schematic the +6 is getting switched on, but on the bottom of the schematic, gnd is getting switched. you should get a meter and play with some transistors to see the results first to get the picture. think of the tranny as an spst relay for now.
if you turn both stamp pins high at the same time, you will soon smell something funny if the room. always have your program turning off one pin before turning the other one on. preferably with at least a few milliseconds pause between the changes to avoid problems.
if you are using the mosfets the gate(same as base with the others) is pin 1 if you are facing the tranny with pins down. put +6 to pin 2(drain) and the motor at pin 3(source) for the high side of the schematic.
look at this link below i found it googling up irf510 hbridge it is the thrid item listed. if you spent 5 minutes on google you would save yourself a lot of headaches [noparse]:)[/noparse] no offense
see page 6 for irf510 hbridge in is most simplest form all you gotta do is find out what pin is gate, drain and source it should be as i stated or on the package: just ignore the pwm part at the bottom of the circuit, run yours to gnd as before.
http://www.dprg.org/tutorials/2003-10a/motorcontrol.pdf
drop the voltage if you are sending more than the motors are rated at.
you could pwm the transistors instead of keeping them high all the time, or write some code that when it is "on", it is really toggling on and off based on your pause length, similar to pwm:
but1 var in1
forward var out2
pausetime var nib
main:
pausetime = 10
if but1 = 1 then motorforward
go to main
motorforward:
do while but1 = 1
forward = 1
pause = pausetime
forward = 0
pause = pausetime
loop
goto main
adjust pausetime till it works but doesnt get too hot, you vould also set a pot with rc on a pin that could translate to pausetime and adjust it by hand to find a sweet spot, or just keep trying numbers.
if you have no sinks, get some small nuts and bolts and attach anything metal, tin foil whatever
Post Edited (willthiswork89) : 7/31/2006 6:30:23 AM GMT
makes no sense that it would be hot when off beats me on that one, possibly wrong connections on source and drain
Where is the Stamp program that you're using to drive this H-Bridge?
Regards,
Bruce Bates
·
Based on your original schematic, a very fundamental thing is being overlooked here with regards to using
bipolar transistors. Your supply voltages are different from each other causing the PNP transistors to never
completely turn off.
This is your original H-Bridge schematic:
http://forums.parallax.com/attachment.php?attachmentid=42686
I can illustrate this in a way that might make more sense if you forget for a moment that the transistor has
a collector and look at it from just the B-E (Base-Emitter) junction. Keep in mind that the B-E junction of a
transistor "looks" like a diode at ALL times regardless of whether the transistor is ON or OFF. Also, remember
that a transistor is a current device, once you have reached the forward bias of the transistor, usually .6V to
.7V, the amount of current you supply to the transistor Base gets amplified across the C-E (Collector Emitter)
junction by the Hfe factor (or gain) of the transistor as long as the current across the C-E junction does not
exceed the transistor ratings.
Based on your schematic, consider the following with just looking at the PNP transistors and with the
exception that you are running the supply with 7.2V....
Q9 Q2 5V (I/O) >--------/\/\----|<----|<------< 7.2V 1K B E B E 1V .6V .6V I = 1mA Q9 Q2 0V (I/O) >--------/\/\----|<----|<------< 7.2V 1K B E B E 6V .6V .6V I = 6mA... assume that the resistor is 1K whether the I/O is set to HIGH (5V) or LOW(0V) there is still an
adequate voltage and current that keeps the PNP transistors "ON". (Q1 and Q7 also apply to this)
Suppose that the Hfe or gain of the transistor is 100, even when the I/O pin is HIGH you have 1mA
of current across the B-E junctions. With an Hfe of 100, the transistor is trying to drive 100mA when
it doesn't need to. This equals HEAT
The HEAT problem that you are also having with your mosfets can also be related to the issue of
having different supply voltages. In either case especially with mosfets, unless you are exercising
them in their linear region or if they are not correctly chosen, they should NOT be getting hot. Bi-polar
transistors will loose heat right off the bat because of the .6V drop across the C-E junction.
For Bipolar transistors:
Suppose your supply is 7.2V and you are trying to drive 500mA. Since you immediately loose .6V, you
end up wasting 300mW of HEAT across the transistor.
P = I * V
P = 500mA * .6V
P = 300mW
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Beau Schwabe
IC Layout Engineer
Parallax, Inc.
I'm not sure exactly what your point is here? The images are difficult to read.
The mention of the 'different' voltage supplies in my earlier post is in reference to the fact that the BS2 is running off of a 5V reference
while the H-Bridge is running off of a 7.2V reference. Not that there is anything wrong with this, it is done all the time, but the circuit
you are using for this is flawed.
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Beau Schwabe
IC Layout Engineer
Parallax, Inc.
You should be more specific and use proper terminology. I'm not sure what you mean exactly by the description you give of your lowest 220 ohm resistor being too strong.
Again, in your statement "...if I put the resistor on the 7.2 supply the motor will not run".
Yes, a transistor Hbridge does have a voltage drop of 1.2V and your motor will "see" 6V as it operates.
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Beau Schwabe
IC Layout Engineer
Parallax, Inc.
Battery->220 Ohm Resistor->Motor Terminal #1
Battery(-)->Motor Terminal #2
this will not run due to a small current loss.
Im concluding that the motor is too large of a current draw to use the hbridge with the Transistors even with a darlington pair. i did although, get the motor to run from 4 IRF510 Mosfets with an extensive ammount of heat