Post by thread:[EE] Hot Chip needs cooling

Hi, I created a small motor control board using a PIC and a SN754410 DNE Motor Driver Chip. I am powering two small motors, and they use about 700ma amps each, when stalled. Each driver of the chip is able to source 1100 ma, so I am in spec. However the chip is getting pretty hot, how do I cool it ? It is a 16 pin DIP. I don't have any heat sinks for DIPs. I do have some that screw on to a TO-220 package. Any way to attach them or any other suggestions welcome. Thanks, Kevin

You could go to your local computer store and get a cooling kit for RAM. there are two kinds: metal sleeves that slide over the entire strip, and those that are just tiny bits of metal that are glued onto each individual RAM chip. You want the latter kind. It won't be an exact fit, but it should work. I do believe they usually come with thermal glue. - Marcel Kevin <spam_OUTkbenTakeThisOuTuniversal.dca.net> wrote: {Quote hidden}> Hi, > I created a small motor control board using a PIC and > a SN754410 DNE Motor Driver Chip. > I am powering two small motors, and they use about 700ma > amps each, when stalled. Each driver of the chip is > able to source 1100 ma, so I am in spec. However the > chip is getting pretty hot, how do I cool it ? It is a 16 > pin DIP. I don't have any heat sinks for DIPs. I do have > some that screw on to a TO-220 package. Any way to attach > them or any other suggestions welcome. > > Thanks, > Kevin >

At 03:09 PM 10/14/2005 -0400, you wrote: >Hi, >I created a small motor control board using a PIC and >a SN754410 DNE Motor Driver Chip. >I am powering two small motors, and they use about 700ma >amps each, when stalled. Each driver of the chip is >able to source 1100 ma, so I am in spec. However the >chip is getting pretty hot, how do I cool it ? It is a 16 >pin DIP. I don't have any heat sinks for DIPs. I do have >some that screw on to a TO-220 package. Any way to attach >them or any other suggestions welcome. > >Thanks, >Kevin Aavid Thermalloy has DIP-16 heatsinks, both slide-on and adhesive. They are not expensive. >Best regards, Spehro Pefhany --"it's the network..." "The Journey is the reward" .....speffKILLspam@spam@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com ->> Inexpensive test equipment & parts http://search.ebay.com/_W0QQsassZspeff

Make your own with a piece of metal folded in a "U" shape the mount on top of the chip, use heat transfer paste in between the metal and the chip. To secure to chip you may need to devise something or possibly bend metal tabs down at the ends of the chip to hold it in place, or make the metal "U" have some other mounting arrangement to the board. Or a cooling fan. _______________________________________ Roy Tauranga New Zealand _______________________________________ > {Original Message removed}

You might try something like these: http://www.hobbyengineering.com/H1538.html On 10/14/05, Kevin <kbenKILLspamuniversal.dca.net> wrote: > Hi, > I created a small motor control board using a PIC and > a SN754410 DNE Motor Driver Chip. > I am powering two small motors, and they use about 700ma > amps each, when stalled. Each driver of the chip is > able to source 1100 ma, so I am in spec. However the > chip is getting pretty hot, how do I cool it ? It is a 16 > pin DIP. I don't have any heat sinks for DIPs. I do have > some that screw on to a TO-220 package. Any way to attach > them or any other suggestions welcome. > > Thanks, > Kevin > > > -

You might try something like these: http://www.hobbyengineering.com/H1538.html On 10/14/05, Kevin <.....kbenKILLspam.....universal.dca.net> wrote: > Hi, > I created a small motor control board using a PIC and > a SN754410 DNE Motor Driver Chip. > I am powering two small motors, and they use about 700ma > amps each, when stalled. Each driver of the chip is > able to source 1100 ma, so I am in spec. However the > chip is getting pretty hot, how do I cool it ? It is a 16 > pin DIP. I don't have any heat sinks for DIPs. I do have > some that screw on to a TO-220 package. Any way to attach > them or any other suggestions welcome. > > Thanks, > Kevin > > > -

Depends on how hot.....but you probably need a heat sink. You can cut them down to size from something larger, and even oversize. Different designs cool more efficiently, but might even need a fan to move air across the heat sink. To attach, you can use thermal epoxy, sil pad or it might even come with thermal tape on it. But whatever you use, make sure its a thermal bond. Double sided tape wont work, as its not designed for thermal bonding and will essentially make the heat sink useless. EraseMEmarcelspam_OUTTakeThisOuTcarrietech.com wrote:You could go to your local computer store and get a cooling kit for RAM. there are two kinds: metal sleeves that slide over the entire strip, and those that are just tiny bits of metal that are glued onto each individual RAM chip. You want the latter kind. It won't be an exact fit, but it should work. I do believe they usually come with thermal glue. - Marcel Kevin wrote: {Quote hidden}> Hi, > I created a small motor control board using a PIC and > a SN754410 DNE Motor Driver Chip. > I am powering two small motors, and they use about 700ma > amps each, when stalled. Each driver of the chip is > able to source 1100 ma, so I am in spec. However the > chip is getting pretty hot, how do I cool it ? It is a 16 > pin DIP. I don't have any heat sinks for DIPs. I do have > some that screw on to a TO-220 package. Any way to attach > them or any other suggestions welcome. > > Thanks, > Kevin >

Kevin wrote: > I created a small motor control board using a PIC and > a SN754410 DNE Motor Driver Chip. > I am powering two small motors, and they use about 700ma > amps each, when stalled. Each driver of the chip is > able to source 1100 ma, so I am in spec. However the > chip is getting pretty hot, how do I cool it ? It is a 16 > pin DIP. I don't have any heat sinks for DIPs. I do have > some that screw on to a TO-220 package. Any way to attach > them or any other suggestions welcome. I saw a bunch of other replies, but I think they are answering the wrong question. I don't know what a SN754410 DNE motor driver chip is (no I'm not going to look it up, that's your job), but it sounds like the wrong tool or maybe its not driven the best way. Your real problem is an inefficient setup. It's probably better to make it more efficient and therefore cooler in the first place than trying to deal with the dissipation of a bad design after the fact. Are the motors DC, brushless DC, something else? What voltage? Unless you've got a very unusual setup, it shouldn't require much waste heat to drive them. Since motors are inductors and have considerable mechanical inertia, they are great candidates for PWM control. The pass elements are always either full on or full off so they dissipate little heat. Most of the losses will come from the voltage drop when on and the transition time while switching between states. Motors work fine with PWM at a few 100 Hz so switching transition times should be minimal. FETs with a few 10s of mOhms on resistance are readily available. Or even bipolars might be fine at such low currents. 200mV saturation x 700mA is only 140mW. In any case we need more information about the motors, the available power supply, and how the motors need to be controlled. ***************************************************************** Embed Inc, embedded system specialists in Littleton Massachusetts (978) 742-9014, http://www.embedinc.com

{Quote hidden}> Kevin wrote: > > I created a small motor control board using a PIC and > > a SN754410 DNE Motor Driver Chip. > > I am powering two small motors, and they use about 700ma > > amps each, when stalled. Each driver of the chip is > > able to source 1100 ma, so I am in spec. However the > > chip is getting pretty hot, how do I cool it ? It is a 16 > > pin DIP. I don't have any heat sinks for DIPs. I do have > > some that screw on to a TO-220 package. Any way to attach > > them or any other suggestions welcome. > > I saw a bunch of other replies, but I think they are answering the wrong > question. I don't know what a SN754410 DNE motor driver chip is (no I'm not > going to look it up, that's your job), but it sounds like the wrong tool or > maybe its not driven the best way. Your real problem is an inefficient > setup. It's probably better to make it more efficient and therefore cooler > in the first place than trying to deal with the dissipation of a bad design > after the fact. > > Are the motors DC, brushless DC, something else? What voltage? Unless > you've got a very unusual setup, it shouldn't require much waste heat to > drive them. Since motors are inductors and have considerable mechanical > inertia, they are great candidates for PWM control. The pass elements are > always either full on or full off so they dissipate little heat. Most of > the losses will come from the voltage drop when on and the transition time > while switching between states. Motors work fine with PWM at a few 100 Hz > so switching transition times should be minimal. FETs with a few 10s of > mOhms on resistance are readily available. Or even bipolars might be fine > at such low currents. 200mV saturation x 700mA is only 140mW. > > In any case we need more information about the motors, the available power > supply, and how the motors need to be controlled. > > They are small DC Motors 1.5v to 3v. 0.18 - 0.25A at no load 0.70A +- 15% at max effic. I am using 4AA NiMh batteries to power the board. I am feeding th SN754410 with the raw voltage. The chip drops 3V as per the data sheet. Right now I am not using PWM I just have a logic high on the enable pin for each driver. The datasheet is here for the SN754410 http://www.pololu.com/products/misc/0024/ but like I said as far as I know I am using the device correctly.

On 10/14/05, Kevin <kbenspam_OUTuniversal.dca.net> wrote: {Quote hidden}> > Kevin wrote: > > > I created a small motor control board using a PIC and > > > a SN754410 DNE Motor Driver Chip. > > > I am powering two small motors, and they use about 700ma > > > amps each, when stalled. Each driver of the chip is > > > able to source 1100 ma, so I am in spec. However the > > > chip is getting pretty hot, how do I cool it ? It is a 16 > > > pin DIP. I don't have any heat sinks for DIPs. I do have > > > some that screw on to a TO-220 package. Any way to attach > > > them or any other suggestions welcome. > > > > In any case we need more information about the motors, the available power > > supply, and how the motors need to be controlled. > > > > > They are small DC Motors 1.5v to 3v. > 0.18 - 0.25A at no load 0.70A +- 15% at max effic. > I am using 4AA NiMh batteries to power the board. I am > feeding th SN754410 with the raw voltage. The chip drops 3V > as per the data sheet. Right now I am not using PWM I just > have a logic high on the enable pin for each driver. > The datasheet is here for the SN754410 > http://www.pololu.com/products/misc/0024/ > but like I said as far as I know I am using the device > correctly. That's lousy! 3V drop * 0.7 A * 2 motors = 4.2 watts dissipated in the chip. Your batteries are spending as much energy warming the chip as they are turning the motors!. And, according to the datasheet, "Continuous total power dissipation at (or below) 25°C free-air temperature (see Note 2) . . . . . . . . 2075 mW" So you are using the chip WAY out of spec. As far as heatsinking this part, the center pins (closest to the die) are ground and they form a heat sink when soldered to your ground plane. But you're going to have a real hard time dissipating 4W. Regards, Mark markrages@gmail -- You think that it is a secret, but it never has been one. - fortune cookie

On Oct 14, 2005, at 1:37 PM, Olin Lathrop wrote: > I saw a bunch of other replies, but I think they are answering the > wrong > question. I don't know what a SN754410 DNE motor driver chip is, but > it sounds like the wrong tool or maybe its not driven the best way. The 754410 is TI's "improved" L293-style quad half-h-bridge chip, with darlington output stages, and the associated significant voltage drops and power dissipation. I don't think it's possible to drive it "improperly" in the linear region, but the specs in the datasheet don't quite match up; total power dissipation is 2W, but there are 4 drivers with ~1V voltage drops, which is 4W at the rated 1A. And even 2W seems like quite a bit for a plastic dip16 package. Do you already have significant copper area attached to the ground pins that are designated for heatsink use as well? If not, that would be your first step. The TI datasheet is unusually useless here; there's better info in the ST sheet: http://www.st.com/stonline/books/pdf/docs/1328.pdf Any chunk of metal is likely to be better than nothing; I'd be tempted to take one of the TO220 heatsinks and some superglue as a first effort. Copper sheet soldered to the designated pins would be better, of course. The 754410 claims to have thermal shutdown. If it's NOT shutting down on you, then just saying "that chip runs hot" MIGHT be good enough, depending on where your project falls on the "hobbyist hack to critically important commercial product" scale. BillW

On 10/14/05, William Chops Westfield <@spam@westfwKILLspammac.com> wrote: > On Oct 14, 2005, at 1:37 PM, Olin Lathrop wrote: > > > I saw a bunch of other replies, but I think they are answering the > > wrong > > question. I don't know what a SN754410 DNE motor driver chip is, but > > it sounds like the wrong tool or maybe its not driven the best way. > > > The 754410 is TI's "improved" L293-style quad half-h-bridge chip, with > darlington output stages, and the associated significant voltage drops > and power dissipation. I don't think it's possible to drive it > "improperly" > in the linear region, but the specs in the datasheet don't quite match > up; total power dissipation is 2W, but there are 4 drivers with ~1V > voltage drops, which is 4W at the rated 1A. And even 2W seems like > quite a bit for a plastic dip16 package. > It's not a question of matching up, you just can't use all four drivers at maximum current at 100% duty cycle. I think datasheet writers like to put the advantageous specs in bold on the front page, and hide the gotchas in the fine print. That's why you must read the whole datasheet, of course. Regards, Mark markrages@gmail -- You think that it is a secret, but it never has been one. - fortune cookie

In message <000001c5d0f7$82d342f0$0100a8c0@roy> "Hopkins" <KILLspamrdhopkinsKILLspamihug.co.nz> wrote: > Make your own with a piece of metal folded in a "U" shape the mount on > top of the chip, use heat transfer paste in between the metal and the > chip. > To secure to chip you may need to devise something or possibly bend > metal tabs down at the ends of the chip to hold it in place, or make the > metal "U" have some other mounting arrangement to the board. Usually with high-power DIPs, the middle <n> pins are grounds and are often thermally connected to the chip itself. I'd solder a copper (or maybe tin if you're a cheapskate) heatsink onto them and rig a fan to move air over the 'sink. All you need to do is bend the edges of the 'sink down, then cut some notches so it doesn't short on the other pins. Later. -- Phil. | Acorn RiscPC600 SA220 64MB+6GB 100baseT RemoveMEphilpemTakeThisOuTphilpem.me.uk | Athlon64 3200+ A8VDeluxe R2 512MB+100GB http://www.philpem.me.uk/ | Panasonic CF-25 Mk.2 Toughbook ... SSC : Spare any Small Change?

Kevin wrote: > They are small DC Motors 1.5v to 3v. > 0.18 - 0.25A at no load 0.70A +- 15% at max effic. > I am using 4AA NiMh batteries to power the board. I am > feeding th SN754410 with the raw voltage. The chip drops 3V > as per the data sheet. Yikes! No wonder it gets hot. You've got about a 5V supply. You certainly don't want the driver elements dropping 60% of the voltage. Your putting more power into the drivers than into the motors. > Right now I am not using PWM I just > have a logic high on the enable pin for each driver. So you only need to switch the motors on and off, not run them a partial power? If so, that's even easier. Use a logic level N-channel FET as a low side switch. Since this is not constantly switching, the switching transition time doesn't matter much. Just drive the gate directly from a PIC pin, source to ground, drain to the motor, and other side of motor to +supply. Don't forget the reverse diode accross the motor and put a small ceramic cap as close as possible directly accross the motor to reduce emissions and other nasties. A small and cheap FET like IRLML2502 would be fine here. It comes is a SOT-23 package, but that doesn't matter since it won't be dissipating any power. 700mA thru 45mOhms is only 22mW. Many other FETs would be fine too. The right NPN could be used too. This is really not a very demanding job for the pass element. ***************************************************************** Embed Inc, embedded system specialists in Littleton Massachusetts (978) 742-9014, http://www.embedinc.com

{Quote hidden}> Kevin wrote: > > They are small DC Motors 1.5v to 3v. > > 0.18 - 0.25A at no load 0.70A +- 15% at max effic. > > I am using 4AA NiMh batteries to power the board. I am > > feeding th SN754410 with the raw voltage. The chip drops 3V > > as per the data sheet. > > Yikes! No wonder it gets hot. You've got about a 5V supply. You certainly > don't want the driver elements dropping 60% of the voltage. Your putting > more power into the drivers than into the motors. > > > Right now I am not using PWM I just > > have a logic high on the enable pin for each driver. > > So you only need to switch the motors on and off, not run them a partial > power? If so, that's even easier. Use a logic level N-channel FET as a low > side switch. Since this is not constantly switching, the switching > transition time doesn't matter much. Just drive the gate directly from a > PIC pin, source to ground, drain to the motor, and other side of motor to > +supply. Don't forget the reverse diode accross the motor and put a small > ceramic cap as close as possible directly accross the motor to reduce > emissions and other nasties. > > A small and cheap FET like IRLML2502 would be fine here. It comes is a > SOT-23 package, but that doesn't matter since it won't be dissipating any > power. 700mA thru 45mOhms is only 22mW. Many other FETs would be fine too. > The right NPN could be used too. This is really not a very demanding job > for the pass element. > Yes, I guess I will have to switch the design to not use that chip. :( I just didn't count on the heat dissipation being such a problem. I eventually wanted to be able to reverse the motors and use PWM to keep them in sync. IE going in a straight line. I just have not gotten that far with the code. ~Kevin

On Sat, 15 Oct 2005, Neil Baylis wrote: > Well, it sounds to me like you're on the right track. Why not just > start using the PWM.? The 754410 should work fine in that mode. > Exactly how hot is it getting now? Were you thinking of using a > current sense resistor to control the current through the motor, or > were you just going to run the PWM open loop? > > Neil > Well, someone calculated 4.2 W and the chip is spec'd at 2.1 W, so pretty damn hot :). I already had the boards made :( so I will try a good heatsink and OPEN Loop PWM. I will try running in a 50% duty cycle any suggetions on freq ? Should I keep it high >20Khz, so the motors don't chatter, or should I use a LOW freq like 200 Hz ? Thanks, Kevin

Experiment till you find a frequency that the motors like, and your ears like ;-). Also, even a small fan will help with the heat, especially if you can, as someone mentioned, solder some copper to the heat sink pins. If your board already has them connected to a healthy ground plane, then just cool the board with a little fan to get the heat away. Does it get too hot to touch? How long does it take to heat up? Neil On 10/15/05, Kevin <spamBeGonekbenspamBeGoneuniversal.dca.net> wrote: {Quote hidden}> On Sat, 15 Oct 2005, Neil Baylis wrote: > > > Well, it sounds to me like you're on the right track. Why not just > > start using the PWM.? The 754410 should work fine in that mode. > > Exactly how hot is it getting now? Were you thinking of using a > > current sense resistor to control the current through the motor, or > > were you just going to run the PWM open loop? > > > > Neil > > > Well, someone calculated 4.2 W and the chip is spec'd at > 2.1 W, so pretty damn hot :). I already had the boards > made :( so I will try a good heatsink and OPEN Loop PWM. > I will try running in a 50% duty cycle any suggetions on > freq ? Should I keep it high >20Khz, so the motors don't > chatter, or should I use a LOW freq like 200 Hz ? > > Thanks, > Kevin > > -

Kevin wrote: > Yes, I guess I will have to switch the design to not use > that chip. :( I just didn't count on the heat > dissipation being such a problem. > I eventually wanted to be able to reverse the motors > and use PWM to keep them in sync. IE going in a straight > line. I just have not gotten that far with the code. That chip is still not the right answer because its voltage drop is more than half you supply. You can make your own H bridge fairly easily. ***************************************************************** Embed Inc, embedded system specialists in Littleton Massachusetts (978) 742-9014, http://www.embedinc.com

Kevin wrote: > I will try running in a 50% duty cycle any suggetions on > freq ? Should I keep it high >20Khz, so the motors don't > chatter, or should I use a LOW freq like 200 Hz ? Lower is better electrically. The mechanical inertia of the motor will filter 200Hz fine. The only reason for going higher is if the motor makes objectionable noises. ***************************************************************** Embed Inc, embedded system specialists in Littleton Massachusetts (978) 742-9014, http://www.embedinc.com

On Sun, 16 Oct 2005, Neil Baylis wrote: > Olin, > > > That chip is still not the right answer because its voltage drop is more > > than half you supply. You can make your own H bridge fairly easily. > > yes, of course it would have been better to start with a different > device, e.g. one that uses power FETs. But he already has boards made. > And his motors are tiny. He may be able to make it work satisfactorily > with what he has, although it won't be optimal. > > Neil Yes, live and learn. In my next board revision I will probably use a Motorola 33887, which is designed around FETS. However, with the suggestions I have received hopefully I can work around the limitations of my current design. No pun intended :) Thanks to All, Kevin

On 10/16/05, Kevin <TakeThisOuTkbenEraseMEspam_OUTuniversal.dca.net> wrote: > > Neil > Yes, live and learn. In my next board revision I will > probably use a Motorola 33887, which is designed around FETS. > However, with the suggestions I have received hopefully I > can work around the limitations of my current design. No pun > intended :) > That's a fancy chip. but it needs at least 5 V. Regards, Mark markrages@gmail -- You think that it is a secret, but it never has been one. - fortune cookie