From: Arnar B. <ar...@gm...> - 2007-03-15 09:23:23
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Hi all, I have a connex 400xm, roboaudiostix and a wifistix-cf. Now - the only way I have to power all this is to power both the roboaudio and the wifistix-cf (through v_batt on the roboaudio) with 5V. My attempts to power only through the roboaudio didn't work when the wifi module turned on. The wifistix gets pretty hot because I'm putting 5V on it. This is simply b/c I have only one power supply. What I would like to do is to build a small unit on a piece of veroboard that I can connect to (preferably) 4 AA or AAA rechargeable cells that should provide between 5 and 6 volts, and have three output pins, +4V, GND and +5V - so that I can power my stack conveniently. I'm a complete novice in this and since the guy at the components-shop is less than helpful, I'd like your opinion on what components I would need for this and any general advice you can spare. thanks, Arnar ps. just fyi I would also put an input on the board for higher voltages which would go through my dimension engineering adj. switching regulator |
From: Daniel O'S. <da...@oz...> - 2007-03-15 09:29:05
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Arnar Birgisson wrote: > What I would like to do is to build a small unit on a piece of > veroboard that I can connect to (preferably) 4 AA or AAA rechargeable > cells that should provide between 5 and 6 volts, and have three output > pins, +4V, GND and +5V - so that I can power my stack conveniently. don't forget, AA rechargeables are only 1.2V though, so four would only equal 4.8V |
From: Arnar B. <ar...@gm...> - 2007-03-15 09:32:28
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On 3/15/07, Daniel O'Shea <da...@oz...> wrote: > Arnar Birgisson wrote: > > What I would like to do is to build a small unit on a piece of > > veroboard that I can connect to (preferably) 4 AA or AAA rechargeable > > cells that should provide between 5 and 6 volts, and have three output > > pins, +4V, GND and +5V - so that I can power my stack conveniently. > > don't forget, AA rechargeables are only 1.2V though, so four would only > equal 4.8V Ok, I have four new ones and they measure 6V freshly charged, is that just right after charging? I don't remember what type they are (I'm at work). Arnar |
From: Arnar B. <ar...@gm...> - 2007-03-16 17:04:06
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Sorry for bumping - but I wanted to try building this over the weekend. Generally I want one convenient unit that I can put some voltage (6-8 volts maybe) either from batteries or my switching regulator and get +5V and +4V suitable to put on the roboaudio and v_batt (for the wifistix-cf and gumstix). +4V regulators seem to be harder to get than +3.3V ones - is 3.3V enough to put on v_batt or does the regulator on the wifistix-cf need more? Dave H. - I was hoping you'd pick this up :o) thanks, Arnar On 3/15/07, Arnar Birgisson <ar...@gm...> wrote: > Hi all, > > I have a connex 400xm, roboaudiostix and a wifistix-cf. Now - the only > way I have to power all this is to power both the roboaudio and the > wifistix-cf (through v_batt on the roboaudio) with 5V. My attempts to > power only through the roboaudio didn't work when the wifi module > turned on. > > The wifistix gets pretty hot because I'm putting 5V on it. This is > simply b/c I have only one power supply. > > What I would like to do is to build a small unit on a piece of > veroboard that I can connect to (preferably) 4 AA or AAA rechargeable > cells that should provide between 5 and 6 volts, and have three output > pins, +4V, GND and +5V - so that I can power my stack conveniently. > > I'm a complete novice in this and since the guy at the components-shop > is less than helpful, I'd like your opinion on what components I would > need for this and any general advice you can spare. > > thanks, > Arnar > > ps. just fyi I would also put an input on the board for higher > voltages which would go through my dimension engineering adj. > switching regulator > |
From: Dave H. <dhy...@gm...> - 2007-03-16 18:30:22
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Hi Arnar, On 3/16/07, Arnar Birgisson <ar...@gm...> wrote: > Sorry for bumping - but I wanted to try building this over the weekend. > > Generally I want one convenient unit that I can put some voltage (6-8 > volts maybe) either from batteries or my switching regulator and get > +5V and +4V suitable to put on the roboaudio and v_batt (for the > wifistix-cf and gumstix). > > +4V regulators seem to be harder to get than +3.3V ones - is 3.3V > enough to put on v_batt or does the regulator on the wifistix-cf need > more? The adjustable one from Dimension Engineering needs about 1.3v of headroom (IIRC) so it should fit the bill of generating 4v out from 6-8v in. <http://www.dimensionengineering.com/DE-SWADJ.htm> Providing 3.3v is too low. The LDO's need a bit of headroom. I seem to recall that 3.5v or so was the minimum. There are lots of adjustable LDOs as well, should you want a non-switching solution. -- Dave Hylands Vancouver, BC, Canada http://www.DaveHylands.com/ |
From: DJ D. <dj...@de...> - 2007-03-16 19:40:53
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"Arnar Birgisson" <ar...@gm...> writes: > +4V regulators seem to be harder to get than +3.3V ones - is 3.3V > enough to put on v_batt or does the regulator on the wifistix-cf need > more? Aside from an adjustable regulator, what I did was put a power diode between +5 and VBATT, which dropped it to about 4.3v for the gumstix. Alternately, you can put a diode on the GND pin of most 3.3v regulators to increase its output by 0.7v. Some even allow a resistor ladder to make them adjustable (upwards), like the 7805. |
From: Arnar B. <ar...@gm...> - 2007-03-17 02:00:30
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Hi there, On 16 Mar 2007 15:40:29 -0400, DJ Delorie <dj...@de...> wrote: > > "Arnar Birgisson" <ar...@gm...> writes: > > +4V regulators seem to be harder to get than +3.3V ones - is 3.3V > > enough to put on v_batt or does the regulator on the wifistix-cf need > > more? > > Aside from an adjustable regulator, what I did was put a power diode > between +5 and VBATT, which dropped it to about 4.3v for the gumstix. What is a power diode? I did a search but couldn't figure it out :o| Arnar |
From: Arnar B. <ar...@gm...> - 2007-03-17 02:01:46
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On 3/16/07, Dave Hylands <dhy...@gm...> wrote: > The adjustable one from Dimension Engineering needs about 1.3v of > headroom (IIRC) so it should fit the bill of generating 4v out from > 6-8v in. > > <http://www.dimensionengineering.com/DE-SWADJ.htm> Yeah, I already have one of these. > Providing 3.3v is too low. The LDO's need a bit of headroom. I seem to > recall that 3.5v or so was the minimum. Ok, then I think I know what I need. I'll let you know how it goes. thanks, Arnar |
From: Arnar B. <ar...@gm...> - 2007-03-17 17:52:22
Attachments:
regulators.gif
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Hi all, I gave this a try, see the attached schematic. Now, it doesn't really work as I expected. I connected the 5V to robobatt and the 4V to v_batt. The gumstix works fine, the L78S05 regulator get's very hot (which I guess is normal - at least I can keep it away from the gumstix) - and it drew 400-550mA from the battery/power source during booting. However, when I measured the current on the 4V connector - it was only about 6mA, and when I tried disconnecting that one nothing went wrong on the gumstix! This was a bit surprising as providing only 5V on robobatt didn't work before, the gumstix would reboot as soon as I turned on the wifi. Am I doing sth. wrong here? Should I just forget about the LM317 and hope the gumstix won't start rebooting again? Arnar |
From: Arnar B. <ar...@gm...> - 2007-03-17 18:07:31
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Hi again, A small addition after more testing: On 3/17/07, Arnar Birgisson <ar...@gm...> wrote: > However, when I measured the current on the 4V connector - it was only > about 6mA, and when I tried disconnecting that one nothing went wrong > on the gumstix! This was a bit surprising as providing only 5V on > robobatt didn't work before, the gumstix would reboot as soon as I > turned on the wifi. It still doesn't work with only 5V on robobatt - it fails on turning on the wifi during booting and reboots. It "works" with the 4V connected on v_batt - but it draws very little current from there, maybe that's just normal? Arnar |
From: Dave H. <dhy...@gm...> - 2007-03-18 03:16:00
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Hi Arnar, > It "works" with the 4V connected on v_batt - but it draws very little > current from there, maybe that's just normal? V_ROBOBATT is run through a 5v regulator, so V_BATT is at 5v. I wouldn't recommend connecting 4v to V_BATT since it might fight with the robostix regulator. I think that the ideal scenario is to put 5.5v on V_ROBOBATT and put 5v on V_BATT. -- Dave Hylands Vancouver, BC, Canada http://www.DaveHylands.com/ |
From: Arnar B. <ar...@gm...> - 2007-03-18 12:01:22
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Hi Dave, On 3/18/07, Dave Hylands <dhy...@gm...> wrote: > V_ROBOBATT is run through a 5v regulator, so V_BATT is at 5v. > > I wouldn't recommend connecting 4v to V_BATT since it might fight with > the robostix regulator. > > I think that the ideal scenario is to put 5.5v on V_ROBOBATT and put > 5v on V_BATT. Ok, I understand. I can adjust the LM317 to 5.5V, shouldn't be a problem. Things were working fine with 5V on both V_ROBOBATT and V_BATT - the wifi module just got pretty hot (so hot I couldn't hold my finger on it for more than a second or two) and I worried that if the whole thing was in an enclosure that things would overheat. I thought that was caused by the 5V on V_BATT. I see now that V_BATT is inevitably 5V - so should I just forget about the heat or provide some sort of heatsinking on the wifi module cover? Does it make a big difference if I put 5V or 5.5V on V_ROBOBATT? Or is it just to be on the safe side? I would like to run this on inexpensive NiMH cells (mostly b/c I have them already and a charger). They have a 1.2V nominal voltage. What does that mean? Does it mean that they maintain 1.2V most of the time? Should 6 cells (7.2V) then be enough if I run everything on 5V - my 5V regulator has a dropout of 6.5-7V for 500mA? Also, what happens when the batteries drop below the regulators drop out - I know the robostix reboots or freezes - but does the regulator keep on drawing current from the batteries? Wikipedia mentions that one should not keep drawing current if you have more than one cell, since one of them might reverse it's polarity and start to feed of the other cells. Do I need some kind of shutoff circtuit to protect the cells from that? There are only two stores with circuit components here in Reykjavik and unfortunately they didn't have any 5V or adjustable LDO regulators :o( Thank you for answering all my stupid questions. Arnar |
From: Dave H. <dhy...@gm...> - 2007-03-18 18:10:43
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Hi Arnar, > Does it make a big difference if I put 5V or 5.5V on V_ROBOBATT? Or is > it just to be on the safe side? If you put 5v on V_ROBOBATT, the ATMega128 will get about 4.5v and the voltage regulator will be struggling, trying to provide 5v output, which it can't do with a 5v input. I don't actually know how much difference it makes. If you were going to put 5v on V_ROBOBATT, then I'd put 4.5v on V_BATT. > I would like to run this on inexpensive NiMH cells (mostly b/c I have > them already and a charger). They have a 1.2V nominal voltage. What > does that mean? Does it mean that they maintain 1.2V most of the time? Sort of. Here's a typical discharge curve for 4 x NiMH batteries: <http://shdesigns.org/batts/battcyc.html> Different battery chemistries have different discharge curves. > Also, what happens when the batteries drop below the regulators drop > out - I know the robostix reboots or freezes - but does the regulator > keep on drawing current from the batteries? You'd need to check the datasheet for the regulator in question. Wikipedia mentions that > one should not keep drawing current if you have more than one cell, > since one of them might reverse it's polarity and start to feed of the > other cells. Do I need some kind of shutoff circtuit to protect the > cells from that? Having the protection circuitry won't hurt. It really depends on what the application is. Are you going to around the robot and notice that the batteries are getting low? Most RC cars don't have battery protection because you can't use the car anymore when the batteries run out, so people generally turn them off. -- Dave Hylands Vancouver, BC, Canada http://www.DaveHylands.com/ |
From: Arnar B. <ar...@gm...> - 2007-03-18 19:25:18
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Hi Dave, On 3/18/07, Dave Hylands <dhy...@gm...> wrote: > Hi Arnar, > > Does it make a big difference if I put 5V or 5.5V on V_ROBOBATT? Or is > > it just to be on the safe side? > > If you put 5v on V_ROBOBATT, the ATMega128 will get about 4.5v and the > voltage regulator will be struggling, trying to provide 5v output, > which it can't do with a 5v input. Ok, sounds like I really should keep to 5.5V on the robostix. > I don't actually know how much difference it makes. If you were going > to put 5v on V_ROBOBATT, then I'd put 4.5v on V_BATT. > > > I would like to run this on inexpensive NiMH cells (mostly b/c I have > > them already and a charger). They have a 1.2V nominal voltage. What > > does that mean? Does it mean that they maintain 1.2V most of the time? > > Sort of. Here's a typical discharge curve for 4 x NiMH batteries: > <http://shdesigns.org/batts/battcyc.html> > > Different battery chemistries have different discharge curves. Thanks, very informative. > > Also, what happens when the batteries drop below the regulators drop > > out - I know the robostix reboots or freezes - but does the regulator > > keep on drawing current from the batteries? > > You'd need to check the datasheet for the regulator in question. > > Wikipedia mentions that > > one should not keep drawing current if you have more than one cell, > > since one of them might reverse it's polarity and start to feed of the > > other cells. Do I need some kind of shutoff circtuit to protect the > > cells from that? > > Having the protection circuitry won't hurt. It really depends on what > the application is. Are you going to around the robot and notice that > the batteries are getting low? Most RC cars don't have battery > protection because you can't use the car anymore when the batteries > run out, so people generally turn them off. I can imagine situations where no-one would be around to shut things off - I'd want to use it for more than R/C stuff. What should I google for to find schematics of such protection circuits and a general idea of how they work? thanks, Arnar |
From: Dave H. <dhy...@gm...> - 2007-03-18 18:54:10
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Hi Arnar, Re: powering V_ROBOBATT and V_BATT. I took another look at the schematics/board layout, and it would be possible to disconnect V_BATT on the robostix from V_BATT going to the gumstix. This would require cutting two traces and soldering in a jumper wire (30 gauge wire-wrap wire). Then you could power your wifistix/gumstix V_BATT with 4v or 3.5v which would keep the wifistix much cooler and run 5.5v into the V_ROBOBATT, and everybody would be happy. If you should want to proceed with this, let me know which revision of robostix you have, so I can tailor the directions. -- Dave Hylands Vancouver, BC, Canada http://www.DaveHylands.com/ |
From: Arnar B. <ar...@gm...> - 2007-03-18 19:27:42
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Hi Dave, On 3/18/07, Dave Hylands <dhy...@gm...> wrote: > Then you could power your wifistix/gumstix V_BATT with 4v or 3.5v > which would keep the wifistix much cooler and run 5.5v into the > V_ROBOBATT, and everybody would be happy. > > If you should want to proceed with this, let me know which revision of > robostix you have, so I can tailor the directions. I'd definately want to at least consider it. I have the roboaudiostix rev. 816. The text on the bottom in full is "62932 RoboAudioStix(tm) PCB00037-R816". Where would the +5V on the "gumstix" header and the v_batt on the serial connectors come from? thanks again, Arnar |
From: Dave H. <dhy...@gm...> - 2007-03-18 23:29:27
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Hi Arnar, > I'd definately want to at least consider it. I have the roboaudiostix > rev. 816. The text on the bottom in full is "62932 RoboAudioStix(tm) > PCB00037-R816". Oh - it's even easier then. On the roboaudiostix, there is just one trace to cut, not soldering required. If you look at this photo: <http://docswiki.gumstix.com/Image:RoboAudio-Top.jpg> at the top left corner of the hi-rose connector is some silkscreen that says CONN60. The 3 pins in the very top left are the V_BATT pins. Just to the left of the top right corner is a via. Basically, if you cut the trace between the via and the hi-rose connector, then you will have isolated the V_BATT on the robostix from the V_BATT going to the gumstix. > Where would the +5V on the "gumstix" header and the v_batt on the > serial connectors come from? They would come from the V_BATT voltage regulator on the roboaudiostix board. The power for the gumstix would come from the V_BATT power connector on the wifistix board. If you're comfortable soldering small things, you could also solder a wire onto the pins on the top left corner of the hirose connector (there is already a trace on the circuit board connecting all 3 pins, so it's not as hard as trying to solder to an individual pin. This wire could be used to provide V_BATT for the gumstix. -- Dave Hylands Vancouver, BC, Canada http://www.DaveHylands.com/ |
From: Arnar B. <ar...@gm...> - 2007-03-19 00:44:03
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Hi Dave, On 3/18/07, Dave Hylands <dhy...@gm...> wrote: > Hi Arnar, > > > I'd definately want to at least consider it. I have the roboaudiostix > > rev. 816. The text on the bottom in full is "62932 RoboAudioStix(tm) > > PCB00037-R816". > > Oh - it's even easier then. On the roboaudiostix, there is just one > trace to cut, not soldering required. > > If you look at this photo: > <http://docswiki.gumstix.com/Image:RoboAudio-Top.jpg> > at the top left corner of the hi-rose connector is some silkscreen > that says CONN60. > > The 3 pins in the very top left are the V_BATT pins. Just to the left > of the top right corner is a via. Basically, if you cut the trace > between the via and the hi-rose connector, then you will have isolated > the V_BATT on the robostix from the V_BATT going to the gumstix. Ok, that shouldn't be to hard. My board doesn't have the "CONN60" silkscreen, the part where it should looks a bit charred - like the hirose was soldered on by hand or something. Here's a photo: http://docswiki.gumstix.com/Image:Roboaudiostix-hirosepower.jpg I circled the trace that I beleive you're talking about - just to make sure I don't do anything stupid (goes to check how much the roboaudio costs :o). > > Where would the +5V on the "gumstix" header and the v_batt on the > > serial connectors come from? > > They would come from the V_BATT voltage regulator on the roboaudiostix board. > > The power for the gumstix would come from the V_BATT power connector > on the wifistix board. > > If you're comfortable soldering small things, you could also solder a > wire onto the pins on the top left corner of the hirose connector > (there is already a trace on the circuit board connecting all 3 pins, > so it's not as hard as trying to solder to an individual pin. This > wire could be used to provide V_BATT for the gumstix. I might need some days to muster the courage for that - but yes, that would be convenient, maybe a right-angle connector to make it stick out from under the gumstix. In the meantime I'm going to see if I can buy a male connector for the power plug on the wifistix. Just for curiosity, is U$32 the regulator for the gumstix? thanks, Arnar |
From: Dave H. <dhy...@gm...> - 2007-03-19 02:32:05
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Hi Arnar, > Ok, that shouldn't be to hard. My board doesn't have the "CONN60" > silkscreen, the part where it should looks a bit charred - like the > hirose was soldered on by hand or something. > > Here's a photo: http://docswiki.gumstix.com/Image:Roboaudiostix-hirosepower.jpg > > I circled the trace that I beleive you're talking about - just to make > sure I don't do anything stupid (goes to check how much the roboaudio > costs :o). Yep - that's the one. > Just for curiosity, is U$32 the regulator for the gumstix? U$50 is the V_BATT regulator. U$32 is a set of 4 pullup resistors. In the RoboAudioTop photo, U$50 is just above the GPIO-3.3v -- Dave Hylands Vancouver, BC, Canada http://www.DaveHylands.com/ |
From: Arnar B. <ar...@gm...> - 2007-03-19 01:54:44
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On 3/19/07, Arnar Birgisson <ar...@gm...> wrote: > > If you're comfortable soldering small things, you could also solder a > > wire onto the pins on the top left corner of the hirose connector > > (there is already a trace on the circuit board connecting all 3 pins, > > so it's not as hard as trying to solder to an individual pin. This > > wire could be used to provide V_BATT for the gumstix. > > I might need some days to muster the courage for that - but yes, that > would be convenient, maybe a right-angle connector to make it stick > out from under the gumstix. In the meantime I'm going to see if I can > buy a male connector for the power plug on the wifistix. I soldered a right angle pin on the backside of the power connector on the wifistix. That was much easier. I haven't cut the trace yet though - I'm going to get my batteries/regulators stuff sorted out first. I tried setting my power supply to 7.2V (the equivalent of 6 NiMHs) and tested the Dimension Engineering adjustable regulator. At that input voltage I can get at most 5.3V output - and that's with no load (just my multimeter). I guess that means running on 6 cells is just not possible without a LDO regulator? Sorry this thread is getting long, I just want to figure out an inexpensive, portable and practical way of powering my particular combo. Hopefully it will benefit others as well. Arnar |
From: Dave H. <dhy...@gm...> - 2007-03-19 02:17:40
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Hi Arnar, > I soldered a right angle pin on the backside of the power connector on > the wifistix. That was much easier. > > I haven't cut the trace yet though - I'm going to get my > batteries/regulators stuff sorted out first. > > I tried setting my power supply to 7.2V (the equivalent of 6 NiMHs) > and tested the Dimension Engineering adjustable regulator. At that > input voltage I can get at most 5.3V output - and that's with no load > (just my multimeter). I guess that means running on 6 cells is just > not possible without a LDO regulator? > > Sorry this thread is getting long, I just want to figure out an > inexpensive, portable and practical way of powering my particular > combo. Hopefully it will benefit others as well. OK - If you're going to cut the trace, then hook up the NiMHs directly to the robostix with no regulator and use the Dimension Engineering regulator to generate 3.7v for plugging into the wifistix power. -- Dave Hylands Vancouver, BC, Canada http://www.DaveHylands.com/ |
From: Arnar B. <ar...@gm...> - 2007-03-19 08:48:06
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Hi Dave, On 3/19/07, Dave Hylands <dhy...@gm...> wrote: > OK - If you're going to cut the trace, then hook up the NiMHs directly > to the robostix with no regulator and use the Dimension Engineering > regulator to generate 3.7v for plugging into the wifistix power. Ok that is a lot easier than my initial plan, we're still talking about 6 cells (7.2V)? Freshly charged they start out at 1.5V so that would be 9V. Maybe 5 cells is better, that gives me 6V with 7.5V at the start. thanks, Arnar |
From: Dave H. <dhy...@gm...> - 2007-03-19 13:47:42
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Hi Arnar, > Ok that is a lot easier than my initial plan, we're still talking > about 6 cells (7.2V)? Freshly charged they start out at 1.5V so that > would be 9V. Maybe 5 cells is better, that gives me 6V with 7.5V at > the start. Yeah - by the time the cells reach 1v (5 x 1v = 5v), they'll be fully discharged, and your robostix will still be able to run. -- Dave Hylands Vancouver, BC, Canada http://www.DaveHylands.com/ |