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Has anyone here gotten a BX-24 to play nicely with servos, off the same power source? I'm using a BX-24 to drive a servo (via a Ferretronics FT639 servo controller chip). If I power the BX24 and a servo from separate power supplies (common ground), every- thing works well together. But if I try powering them from the same power source (either a regulated power supply, or batteries) the BX24 will reset every few servo movements. I have a 47uf capacitor across the power leads, and have experimented with different other values, but to no avail. Also, I've tried a couple of different servo models, the problem occurs with both types (Hitec HS81 and HS50's). Ironically, very large servo motions don't pose a problem - it's when the servo is moved just a few degrees that the BX24 resets. So I think it's noise, rather than a voltage drop situation. Any ideas?

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Vince, Its called a brown-out reset. You can do it but you have to take precautions. For an example of one way to do this check my website out on the 2313 robot controller board link. Look at the diode between the battery and motors and the regulator for the microcontroller. I use a variation of this circuit on all my controller boards. http://www.frii.com/~dlc/botlinks.htm have fun, DLC Vince Pearman wrote: > > Has anyone here gotten a BX-24 to play nicely with servos, off the > same power source? I'm using a BX-24 to drive a servo (via a > Ferretronics FT639 servo controller chip). If I power the BX24 and > a servo from separate power supplies (common ground), every- > thing works well together. But if I try powering them from the same > power source (either a regulated power supply, or batteries) the > BX24 will reset every few servo movements. I have a 47uf capacitor > across the power leads, and have experimented with different other > values, but to no avail. Also, I've tried a couple of different servo > models, the problem occurs with both types (Hitec HS81 and HS50's). > > Ironically, very large servo motions don't pose a problem - it's when > the servo is moved just a few degrees that the BX24 resets. So I > think it's noise, rather than a voltage drop situation. > > Any ideas? > > Yahoo! Groups Sponsor > ADVERTISEMENT > > Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service. -- --------------------------------------------------------------------- * Dennis Clark Mechanical Engineering Behavior Based Robotics * * www.frii.com/~dlc/botlinks.htm * ---------------------------------------------------------------------

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Vince, I am running my BX-24 breadboard system from a 5V 2.3amp wall transformer. I can run a HS-55 from the same power supply and creating the pulse train directly from a BX-24 pin with a 470 ohm resister between them. On the other hand I am having troubles driving a motor behind an ILFZ44N power MOSFET. My system constantly resets when it gets to about 25% power. The motor is powered with a 9volt battery with common grounds. I will be interested in what people have to say about your problem. Good luck, Mark --- Vince Pearman <> wrote: > Has anyone here gotten a BX-24 to play nicely with > servos, off the > same power source? I'm using a BX-24 to drive a > servo (via a > Ferretronics FT639 servo controller chip). If I > power the BX24 and > a servo from separate power supplies (common > ground), every- > thing works well together. But if I try powering > them from the same > power source (either a regulated power supply, or > batteries) the > BX24 will reset every few servo movements. I have a > 47uf capacitor > across the power leads, and have experimented with > different other > values, but to no avail. Also, I've tried a couple > of different servo > models, the problem occurs with both types (Hitec > HS81 and HS50's). > > Ironically, very large servo motions don't pose a > problem - it's when > the servo is moved just a few degrees that the BX24 > resets. So I > think it's noise, rather than a voltage drop > situation. > > Any ideas? __________________________________________________

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Mark 1.Common ground. Separate ground lead for the motor and for the bx24 back to the main 0v connection so that the motor current and the bx24 current don't share any part of the 0v lead. This is to prevent so called earth loops. What happens is current transients in the motor earth are impressed on the earth for the bx24 and cause the 0v pin of the bx24 to rise. If you run the motor earth back to the 0v pin of the motor power supply, and the bx24 0v lead back to the 9v battery -ve, then tie the two earths together with a separate wire, you will get around this problem. 2. Diode in series with the +ve to the bx24 and a 100uF or similar accross the BX24 supply, AND a 0.1uF. 3. Separate voltage regulator ( 12v or 15v) for the bx24, in addition to the internal one, with its own input and output capacitors.. Mark Newell wrote: > Vince, > > I am running my BX-24 breadboard system from a 5V > 2.3amp wall transformer. I can run a HS-55 from the > same power supply and creating the pulse train > directly from a BX-24 pin with a 470 ohm resister > between them. On the other hand I am having troubles > driving a motor behind an ILFZ44N power MOSFET. My > system constantly resets when it gets to about 25% > power. The motor is powered with a 9volt battery with > common grounds. I will be interested in what people > have to say about your problem. > > Good luck, > Mark > --- Vince Pearman <> wrote: > > Has anyone here gotten a BX-24 to play nicely with > > servos, off the > > same power source? I'm using a BX-24 to drive a > > servo (via a > > Ferretronics FT639 servo controller chip). If I > > power the BX24 and > > a servo from separate power supplies (common > > ground), every- > > thing works well together. But if I try powering > > them from the same > > power source (either a regulated power supply, or > > batteries) the > > BX24 will reset every few servo movements. I have a > > 47uf capacitor > > across the power leads, and have experimented with > > different other > > values, but to no avail. Also, I've tried a couple > > of different servo > > models, the problem occurs with both types (Hitec > > HS81 and HS50's). > > > > Ironically, very large servo motions don't pose a > > problem - it's when > > the servo is moved just a few degrees that the BX24 > > resets. So I > > think it's noise, rather than a voltage drop > > situation. > > > > Any ideas? > > > > > > __________________________________________________ > > Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service. [Non-text portions of this message have been removed]

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Well it works for me with two motors and two servos. I'm running two servos and two motors (LM298). I have a small 12 volt battery, with a voltage regulator for the BX24. The motors run direct off the battery via the LM298 chip. The BS24 and servos get their power off the voltage regulator. I am using heavier wire (24 guage) than the little pukey thin stuff for ground and V+ that you normally see people using. On the logic board I have several electrolytics, and bypass caps, plus caps on the motors as well. Your probably getting a surge from the motors that "brown's out" the BX24. Under load a servo can draw 500ma to over 1 amp if it stalls. -----Original Message----- From: Vince Pearman [mailto:] Sent: Monday, January 28, 2002 7:56 PM To: Subject: [BasicX] BX-24 + servo problem Has anyone here gotten a BX-24 to play nicely with servos, off the same power source? I'm using a BX-24 to drive a servo (via a Ferretronics FT639 servo controller chip). If I power the BX24 and a servo from separate power supplies (common ground), every- thing works well together. But if I try powering them from the same power source (either a regulated power supply, or batteries) the BX24 will reset every few servo movements. I have a 47uf capacitor across the power leads, and have experimented with different other values, but to no avail. Also, I've tried a couple of different servo models, the problem occurs with both types (Hitec HS81 and HS50's). Ironically, very large servo motions don't pose a problem - it's when the servo is moved just a few degrees that the BX24 resets. So I think it's noise, rather than a voltage drop situation. Any ideas? Yahoo! Groups Sponsor ADVERTISEMENT Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service. [Non-text portions of this message have been removed]

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Neil, Thanks, I thought I had the grounds meeting at the "original" ground but it turned out it was common with the BX-24. I have researched the simple process of making a 6volt regulator for the BX-24 using a 7806 and I have found numerous examples using a diode on the input to the 7806 to prevent reversing the source polarity, and a cap from source to ground, a cap on the 7806 output to ground and diode from the 7806 output to ground and a serial diode on the 7806 output. The other end of simplicity had a 7806 and 2 caps. If you wouldn't mind could you describe your ideal voltage regulator using a 7806 and what and why the values of caps and diodes. I hope others could gain from this information also. Thanks, Mark --- Neil Jepsen <> wrote: > Mark > 1.Common ground. Separate ground lead > for the motor and for > the bx24 back to the main 0v connection so that the > motor current and > the bx24 current don't share any part of the 0v > lead. This is to prevent > so called earth loops. What happens is current > transients in the motor > earth are impressed on the earth for the bx24 and > cause the 0v pin of > the bx24 to rise. If you run the motor earth back to > the 0v pin of the > motor power supply, and the bx24 0v lead back to the > 9v battery -ve, > then tie the two earths together with a separate > wire, you will get > around this problem. > 2. Diode in series with the +ve to the > bx24 and a 100uF or > similar accross the BX24 supply, AND a 0.1uF. > 3. Separate voltage regulator ( 12v or > 15v) for the bx24, > in addition to the internal one, with its own input > and output > capacitors.. > > Mark Newell wrote: > > > Vince, > > > > I am running my BX-24 breadboard system from a 5V > > 2.3amp wall transformer. I can run a HS-55 from > the > > same power supply and creating the pulse train > > directly from a BX-24 pin with a 470 ohm resister > > between them. On the other hand I am having > troubles > > driving a motor behind an ILFZ44N power MOSFET. > My > > system constantly resets when it gets to about 25% > > power. The motor is powered with a 9volt battery > with > > common grounds. I will be interested in what > people > > have to say about your problem. > > > > Good luck, > > Mark > > --- Vince Pearman <> > wrote: > > > Has anyone here gotten a BX-24 to play nicely > with > > > servos, off the > > > same power source? I'm using a BX-24 to drive a > > > servo (via a > > > Ferretronics FT639 servo controller chip). If I > > > power the BX24 and > > > a servo from separate power supplies (common > > > ground), every- > > > thing works well together. But if I try > powering > > > them from the same > > > power source (either a regulated power supply, > or > > > batteries) the > > > BX24 will reset every few servo movements. I > have a > > > 47uf capacitor > > > across the power leads, and have experimented > with > > > different other > > > values, but to no avail. Also, I've tried a > couple > > > of different servo > > > models, the problem occurs with both types > (Hitec > > > HS81 and HS50's). > > > > > > Ironically, very large servo motions don't pose > a > > > problem - it's when > > > the servo is moved just a few degrees that the > BX24 > > > resets. So I > > > think it's noise, rather than a voltage drop > > > situation. > > > > > > Any ideas? > > > > > > > > > > > > > > > __________________________________________________ > > > > Your use of Yahoo! Groups is subject to the Yahoo! > Terms of Service. > [Non-text portions of this message have been > removed] __________________________________________________

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Mark There are two alternatives to powering the BX24. You can supply 5.5 - 16v to pin 24, using an off-board regulator, or you can supply 5.0v to pin 21 and leave pin 24 unconnected. For best noise immunity I would supply pin 24 with at least 10v as this will give the on-board regulator better head room. As to capacitors: Imagine we have a DC supply, providing say 15v, via a series diode to a 12v regulator, which is supplying pin24 of the bx24. The regulator requires capacitors to ground on its input, and its output. On the input, I would use at leasst 100uF, preferably 1000uF and one or two 0.1uF in parallel, and clsoe to ther regulator. On the output side, I would use 10- 100uF tantalum and the 0.1uF caps. Why? The larger electrolytic is there to soak up large downward transients. When your motor turns on, the input voltage to the BX24 line will drop and may drop below 5v momentarily. The 1000 uF is there to make up the current difference during the transient or brown-out. Unfortunately electros have a rather large internal resistance, and are therefore slow at this task ( T = RC).The 0.1uF caps are much faster and can supply large amounts of current, but only for very short times, so they take out the very short sharp transients. A tanatalum is much quicker ( lower internal resistance) than a standard electro. The regulator should handle upward transients, and prevent these from getting to the BX24 regulator. Typically a 3t regulator has about 60dB of ripple rejection at 120 Hz and 20 dB at 1MHz, so they are quite good. Also, a 1v "step" on the input will only allow about 5mV step in the output. You should also have a few 0.1uF caps scattered around on the PCB on the BX24 supply lines to soak up this noise. There should definitely be an 0.1uF next to pin 24 on the bx24 PCB. The series diode is to prevent the caps from being discharged by the motor, and also, to protect the bx24 should you connect it up the wrong way. (important) I know the book says that the BX24 internal regulator is a low drop-out regulator, and can operate at 6v, but I am more comfortable with some headspace, and would replace your 7806 with a 7812 and supply pin 24 with 12v. You can boost the output of the 7806 with a couple of diodes in the common lead, but I'm not sure whether this degrades the regulator performance. neil Mark Newell wrote: > Neil, > > Thanks, I thought I had the grounds meeting at the > "original" ground but it turned out it was common with > the BX-24. I have researched the simple process of > making a 6volt regulator for the BX-24 using a 7806 > and I have found numerous examples using a diode on > the input to the 7806 to prevent reversing the source > polarity, and a cap from source to ground, a cap on > the 7806 output to ground and diode from the 7806 > output to ground and a serial diode on the 7806 > output. The other end of simplicity had a 7806 and 2 > caps. If you wouldn't mind could you describe your > ideal voltage regulator using a 7806 and what and why > the values of caps and diodes. I hope others could > gain from this information also. > > Thanks, > Mark > > --- Neil Jepsen <> wrote: > > Mark > > 1.Common ground. Separate ground lead > > for the motor and for > > the bx24 back to the main 0v connection so that the > > motor current and > > the bx24 current don't share any part of the 0v > > lead. This is to prevent > > so called earth loops. What happens is current > > transients in the motor > > earth are impressed on the earth for the bx24 and > > cause the 0v pin of > > the bx24 to rise. If you run the motor earth back to > > the 0v pin of the > > motor power supply, and the bx24 0v lead back to the > > 9v battery -ve, > > then tie the two earths together with a separate > > wire, you will get > > around this problem. > > 2. Diode in series with the +ve to the > > bx24 and a 100uF or > > similar accross the BX24 supply, AND a 0.1uF. > > 3. Separate voltage regulator ( 12v or > > 15v) for the bx24, > > in addition to the internal one, with its own input > > and output > > capacitors.. > > > > Mark Newell wrote: > > > > > Vince, > > > > > > I am running my BX-24 breadboard system from a 5V > > > 2.3amp wall transformer. I can run a HS-55 from > > the > > > same power supply and creating the pulse train > > > directly from a BX-24 pin with a 470 ohm resister > > > between them. On the other hand I am having > > troubles > > > driving a motor behind an ILFZ44N power MOSFET. > > My > > > system constantly resets when it gets to about 25% > > > power. The motor is powered with a 9volt battery > > with > > > common grounds. I will be interested in what > > people > > > have to say about your problem. > > > > > > Good luck, > > > Mark > > > --- Vince Pearman <> > > wrote: > > > > Has anyone here gotten a BX-24 to play nicely > > with > > > > servos, off the > > > > same power source? I'm using a BX-24 to drive a > > > > servo (via a > > > > Ferretronics FT639 servo controller chip). If I > > > > power the BX24 and > > > > a servo from separate power supplies (common > > > > ground), every- > > > > thing works well together. But if I try > > powering > > > > them from the same > > > > power source (either a regulated power supply, > > or > > > > batteries) the > > > > BX24 will reset every few servo movements. I > > have a > > > > 47uf capacitor > > > > across the power leads, and have experimented > > with > > > > different other > > > > values, but to no avail. Also, I've tried a > > couple > > > > of different servo > > > > models, the problem occurs with both types > > (Hitec > > > > HS81 and HS50's). > > > > > > > > Ironically, very large servo motions don't pose > > a > > > > problem - it's when > > > > the servo is moved just a few degrees that the > > BX24 > > > > resets. So I > > > > think it's noise, rather than a voltage drop > > > > situation. > > > > > > > > Any ideas? > > > > > > > > > > > > > > > > > > > > > __________________________________________________ > > > > > > Your use of Yahoo! Groups is subject to the Yahoo! > > Terms of Service. > > > > > > [Non-text portions of this message have been > > removed] > > > > __________________________________________________ > > Yahoo! Groups Sponsor ADVERTISEMENT > > Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service. [Non-text portions of this message have been removed]

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Thanks to everyone for the helpful tips - I have it running reliably now, after adding a separate 7805 to provide power for the servo (the BX24 runs off of a 7806). Ideally, I'd like the whole setup to run directly off 6 volts without the need for a regulator, so I'll be experimenting with some of the filtering suggestions mentioned here. I'll post the results when I get there. Thanks again!

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Neil, Thank you for the very excellent and detailed response. It was just what I was looking for. I am trying to learn the EE side of microprocessor systems and your answer goes a very long way to help understanding. Thanks again for sharing the time and knowledge. Mark --- Neil Jepsen <> wrote: > Mark > There are two alternatives to powering > the BX24. You can > supply 5.5 - 16v to pin 24, using an off-board > regulator, or you can > supply 5.0v to pin 21 and leave pin 24 unconnected. > For best noise immunity I would supply pin 24 with > at least 10v as this > will give the on-board regulator better head room. > As to capacitors: Imagine we have a DC supply, > providing say 15v, via a > series diode to a 12v regulator, which is supplying > pin24 of the bx24. > The regulator requires capacitors to ground on its > input, and its > output. On the input, I would use at leasst 100uF, > preferably 1000uF and > one or two 0.1uF in parallel, and clsoe to ther > regulator. On the output > side, I would use 10- 100uF tantalum and the 0.1uF > caps. Why? The > larger electrolytic is there to soak up large > downward transients. When > your motor turns on, the input voltage to the BX24 > line will drop and > may drop below 5v momentarily. The 1000 uF is there > to make up the > current difference during the transient or > brown-out. Unfortunately > electros have a rather large internal resistance, > and are therefore slow > at this task ( T = RC).The 0.1uF caps are much > faster and can supply > large amounts of current, but only for very short > times, so they take > out the very short sharp transients. A tanatalum is > much quicker ( lower > internal resistance) than a standard electro. The > regulator should > handle upward transients, and prevent these from > getting to the BX24 > regulator. Typically a 3t regulator has about 60dB > of ripple rejection > at 120 Hz and 20 dB at 1MHz, so they are quite good. > Also, a 1v "step" > on the input will only allow about 5mV step in the > output. You should > also have a few 0.1uF caps scattered around on the > PCB on the BX24 > supply lines to soak up this noise. There should > definitely be an 0.1uF > next to pin 24 on the bx24 PCB. > The series diode is to prevent the caps from being > discharged by the > motor, and also, to protect the bx24 should you > connect it up the wrong > way. (important) > I know the book says that the BX24 internal > regulator is a low drop-out > regulator, and can operate at 6v, but I am more > comfortable with some > headspace, and would replace your 7806 with a 7812 > and supply pin 24 > with 12v. You can boost the output of the 7806 with > a couple of diodes > in the common lead, but I'm not sure whether this > degrades the regulator > performance. > neil > Mark Newell wrote: > > > Neil, > > > > Thanks, I thought I had the grounds meeting at the > > "original" ground but it turned out it was common > with > > the BX-24. I have researched the simple process > of > > making a 6volt regulator for the BX-24 using a > 7806 > > and I have found numerous examples using a diode > on > > the input to the 7806 to prevent reversing the > source > > polarity, and a cap from source to ground, a cap > on > > the 7806 output to ground and diode from the 7806 > > output to ground and a serial diode on the 7806 > > output. The other end of simplicity had a 7806 and > 2 > > caps. If you wouldn't mind could you describe > your > > ideal voltage regulator using a 7806 and what and > why > > the values of caps and diodes. I hope others could > > gain from this information also. > > > > Thanks, > > Mark > > > > --- Neil Jepsen <> wrote: > > > Mark > > > 1.Common ground. Separate ground > lead > > > for the motor and for > > > the bx24 back to the main 0v connection so that > the > > > motor current and > > > the bx24 current don't share any part of the 0v > > > lead. This is to prevent > > > so called earth loops. What happens is current > > > transients in the motor > > > earth are impressed on the earth for the bx24 > and > > > cause the 0v pin of > > > the bx24 to rise. If you run the motor earth > back to > > > the 0v pin of the > > > motor power supply, and the bx24 0v lead back to > the > > > 9v battery -ve, > > > then tie the two earths together with a separate > > > wire, you will get > > > around this problem. > > > 2. Diode in series with the +ve to > the > > > bx24 and a 100uF or > > > similar accross the BX24 supply, AND a 0.1uF. > > > 3. Separate voltage regulator ( 12v > or > > > 15v) for the bx24, > > > in addition to the internal one, with its own > input > > > and output > > > capacitors.. > > > > > > Mark Newell wrote: > > > > > > > Vince, > > > > > > > > I am running my BX-24 breadboard system from a > 5V > > > > 2.3amp wall transformer. I can run a HS-55 > from > > > the > > > > same power supply and creating the pulse train > > > > directly from a BX-24 pin with a 470 ohm > resister > > > > between them. On the other hand I am having > > > troubles > > > > driving a motor behind an ILFZ44N power > MOSFET. > > > My > > > > system constantly resets when it gets to about > 25% > > > > power. The motor is powered with a 9volt > battery > > > with > > > > common grounds. I will be interested in what > > > people > > > > have to say about your problem. > > > > > > > > Good luck, > > > > Mark > > > > --- Vince Pearman <> > > > wrote: > > > > > Has anyone here gotten a BX-24 to play > nicely > > > with > > > > > servos, off the > > > > > same power source? I'm using a BX-24 to > drive a > > > > > servo (via a > > > > > Ferretronics FT639 servo controller chip). > If I > > > > > power the BX24 and > > > > > a servo from separate power supplies (common > > > > > ground), every- > > > > > thing works well together. But if I try > > > powering > > > > > them from the same > > > > > power source (either a regulated power > supply, > > > or > > > > > batteries) the > > > > > BX24 will reset every few servo movements. > I > > > have a > > > > > 47uf capacitor > > > > > across the power leads, and have > experimented > > > with > > > > > different other > > > > > values, but to no avail. Also, I've tried a > > > couple > > > > > of different servo > > > > > models, the problem occurs with both types > > > (Hitec > > > > > HS81 and HS50's). > === message truncated === __________________________________________________

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