Alt-BEAM Archive

Message #06119



To: beam@sgiblab.sgi.com
From: Scott Burns s-burns@uiuc.edu
Date: Fri, 17 Sep 1999 09:24:35 -0500
Subject: [alt-beam] Re: power_smart_head fest


I removed the cap near the motor and it ran one way or the other as
expected. When the LDRs were equally illuminated, the motor stopped and the
circuit consumed over 50mA while the motor received a rapidly alternating
current. This is all as you said it would be.

But when I replaced the cap and removed the 5.6M resistor, I saw no change
in behavior. The motor snoozed regardless of how I illuminated the LDRs,
the curcuit consumed only a few mA, and the scope traces looked much like
those I posted on the web page.

At 06:06 PM 9/16/99 -0700, you wrote:
>Very impressive presentation of a non-starter circuit.
>
>Well we must do something about that!
>
>I will duplicate the protoboard layout precisely and report back with some
>fine adjustments but in the mean time experiment a little!
>
>Going from memory and my reasonably good understanding of the circuit, the
>simplest way to get some action is to remove the 0.01 cap closest to the
>motor. That will turn the circuit into a monocore head with the motor
>buzzing but not moving when both LDRs are lit and turning left or right with
>a speed proportional to the LDR imbalance. Very similar to the Bicore head
>but unlike the Bicore, no diodes are needed when using LDRs (note to Rob!)
>Next put the 0.01 cap back and remove 5.6M. The circuit will still "snooze"
>when the LDRs are carefully balanced but will now turn continuously left or
>right when unbalanced. The final adjustment is to strike a compromise
>between these two behaviours and have it snooze when balanced, turn slowly
>when slightly unbalanced and turn fast when greatly unbalanced.
>
> BTW The 1K resistors are optional when using medium resistance LDRs (like
>the ones you are using which look like the current model of Radio Shack
>LDRs). So for most applications, the circuit can be simplified by removing
>the 1K resistors and connecting the LDRs directly across the 5V supply.
>
>More to come....
>
>regards
>
> Wilf Rigter mailto:wilf.rigter@powertech.bc.ca
> tel: (604)590-7493
> fax: (604)590-3411
>
> > -----Original Message-----
> > From: Scott Burns [SMTP:s-burns@uiuc.edu]
> > Sent: Thursday, September 16, 1999 9:16 AM
> > To: beam@sgiblab.sgi.com
> > Subject: RE: power_smart_head fest
> >
> > At 06:12 PM 9/10/99 -0700, you wrote:
> > >Hello Scott,
> > >
> > >Tell us more: what components? which schematic? what motor? matched LDRs?
> > >
> > >best regards
> > >
> > > Wilf Rigter mailto:wilf.rigter@powertech.bc.ca
> > >
> >
> > OK, I've described it in detail (including scope readings) at
> >
> > http://www.designbyalgorithm.com/circuit.htm
> >
> > > > -----Original Message-----
> > > > From: Scott Burns [SMTP:s-burns@uiuc.edu]
> > > > Sent: Friday, September 10, 1999 7:05 AM
> > > > To: beam@sgiblab.sgi.com
> > > > Subject: Re: power_smart_head fest
> > > >
> > > > Dear Wilf:
> > > >
> > > > The virtual beam workshop sounds great. I tried building the PSH and
> > was
> > > > able to get the square waves to the motor to change duty cycle with
> > > > changes
> > > > in relative LDR illumination, but they were always in phase. The motor
> > > > never saw a voltage differential across it. I'm anxious to figure out
> > what
> > > >
> > > > I did wrong.
> > > >
> > > > Regards, Scott
> > > >
> > > >
> >
> > ------------------------------------------
> > Prof. Scott A. Burns
> > Dept of General Engineering and Civil Engineering
> > University of Illinois at Urbana-Champaign
> > 104 S. Mathews, Urbana, IL 61801
> > Phone 217/333-1618, FAX 217/244-5705

------------------------------------------
Prof. Scott A. Burns
Dept of General Engineering and Civil Engineering
University of Illinois at Urbana-Champaign
104 S. Mathews, Urbana, IL 61801
Phone 217/333-1618, FAX 217/244-5705



6120 Fri, 17 Sep 1999 09:59:28 -0500 [alt-beam] Re: So...what did I miss? beam@sgiblab.sgi.com Richard Piotter Well, I didn't know they'd released it yet. They told be they were going
to. Anyway, their Quadrapod Kit (body and servos) is $295., and even
without servos, I think It was 195. I LITERALY can't spend too much. I
actualy canceled long distance to save money. College has it's costs!
Put simply, I can't afford it, but someday, when I have cash to spare,
I'll get the Quadrapod kit. That will have to wait though, until I have
cash to spend.

Bob Shannon wrote:
>
> Richard Piotter wrote:
> >
> > Speaking of Spyder, I found the same assembly Mark T used for the eyes
> > (asthetic definitely, functional??? I don't know). They look very nice,
> > but I may save them for Quadrapod (lens assemblys that nice don't pop up
> > every day!). I also have a micro camera and a matching 2.4 GHz video
> > transmitter and reciever. I look forward to the day that I can begin
> > worknig on the mechanical aspects of Quadrapod. I haven't done anything
> > cause I can't afford the motors and mechanical stuff. Easiest would be
> > to buy a Lynxmotion Hexapod II and hack it up, but $375 is over my price
> > margin! $100 is over my price margin! :)
>
> Why not buy a Lynxmotion Quadrapod kit? (Its new)

--


Richard Piotter
richfile@rconnect.com

The Richfiles Robotics & TI web page:
http://richfiles.calc.org

For the BEAM Robotics list:
BEAM Robotics Tek FAQ
http://people.ne.mediaone.net/bushbo/beam/FAQ.html



6121 Fri, 17 Sep 1999 08:51:19 -0700 [alt-beam] Re: power_smart_head fest "'beam@sgiblab.sgi.com'" Wilf Rigter Well.....

I have protoboarded the ps head exactly the way it is shown on your webpage
and it works perfectly for me. I have tried a variety of chips and
component values and it just keeps on working. It certainly is more
sensitive with photodiodes and more active with the 1K resistors removed but
LDRs with or without 1K resistors work fine too. Are you certain of the
component values? Capacitors can have a wide tolerance but even so that
should not produce the problem you show. If the LDRs are very low value (100
ohm in moderate light) the 1K resistors may interfere. If the 1K resistors
are 10K that would also explain the behaviour in bright light. One other
experiment is to swap the 10M and 5.6M resistors: note the difference in
behaviour in low light and when the LDRs are balanced. The best "tuning" of
the circuit ended up with the 5.6M resistor changed to 10M and the 10M
resistor changed to 9.1M. The absolute values are less important than the
ratios and the original circuit works quite well but is somewhat
conservative (and snoozy) compared to the fine tuned values.

One more comment: the PS head V1 is robust and stable and the high frequency
problem I referred to earlier is easily controlled with a 0.1 uf cap across
the motor. The PS head V2 and V3 circuits require critical adjustments and
are not recommended for the faint of heart. Since the objective of the later
versions was to control high frequencies, the much simpler V1 with a cap
across the motor is the preferred circuit.



Wilf Rigter mailto:wilf.rigter@powertech.bc.ca
tel: (604)590-7493
fax: (604)590-3411

> -----Original Message-----
> From: Scott Burns [SMTP:s-burns@uiuc.edu]
> Sent: Thursday, September 16, 1999 9:16 AM
> To: beam@sgiblab.sgi.com
> Subject: RE: power_smart_head fest
>
> At 06:12 PM 9/10/99 -0700, you wrote:
> >Hello Scott,
> >
> >Tell us more: what components? which schematic? what motor? matched LDRs?
> >
> >best regards
> >
> > Wilf Rigter mailto:wilf.rigter@powertech.bc.ca
> >
>
> OK, I've described it in detail (including scope readings) at
>
> http://www.designbyalgorithm.com/circuit.htm
>
> > > -----Original Message-----
> > > From: Scott Burns [SMTP:s-burns@uiuc.edu]
> > > Sent: Friday, September 10, 1999 7:05 AM
> > > To: beam@sgiblab.sgi.com
> > > Subject: Re: power_smart_head fest
> > >
> > > Dear Wilf:
> > >
> > > The virtual beam workshop sounds great. I tried building the PSH and
> was
> > > able to get the square waves to the motor to change duty cycle with
> > > changes
> > > in relative LDR illumination, but they were always in phase. The motor
> > > never saw a voltage differential across it. I'm anxious to figure out
> what
> > >
> > > I did wrong.
> > >
> > > Regards, Scott
> > >
> > >
>
> ------------------------------------------
> Prof. Scott A. Burns
> Dept of General Engineering and Civil Engineering
> University of Illinois at Urbana-Champaign
> 104 S. Mathews, Urbana, IL 61801
> Phone 217/333-1618, FAX 217/244-5705



6122 Fri, 17 Sep 1999 17:41:03 GMT [alt-beam] Re: power_smart_head fest beam@sgiblab.sgi.com "Jason -"


>From: Wilf Rigter
>Reply-To: beam@sgiblab.sgi.com
>To: "'beam@sgiblab.sgi.com'"
>Subject: RE: power_smart_head fest
>Date: Fri, 17 Sep 1999 08:51:19 -0700
>
>Well.....
>
>I have protoboarded the ps head exactly the way it is shown on your webpage
>and it works perfectly for me. I have tried a variety of chips and
>component values and it just keeps on working. It certainly is more
>sensitive with photodiodes and more active with the 1K resistors removed
>but
>LDRs with or without 1K resistors work fine too. Are you certain of the
>component values? Capacitors can have a wide tolerance but even so that
>should not produce the problem you show. If the LDRs are very low value
>(100
>ohm in moderate light) the 1K resistors may interfere. If the 1K resistors
>are 10K that would also explain the behaviour in bright light. One other
>experiment is to swap the 10M and 5.6M resistors: note the difference in
>behaviour in low light and when the LDRs are balanced. The best "tuning" of
>the circuit ended up with the 5.6M resistor changed to 10M and the 10M
>resistor changed to 9.1M. The absolute values are less important than the
>ratios and the original circuit works quite well but is somewhat
>conservative (and snoozy) compared to the fine tuned values.
>
>One more comment: the PS head V1 is robust and stable and the high
>frequency
>problem I referred to earlier is easily controlled with a 0.1 uf cap across
>the motor. The PS head V2 and V3 circuits require critical adjustments and
>are not recommended for the faint of heart. Since the objective of the
>later
>versions was to control high frequencies, the much simpler V1 with a cap
>across the motor is the preferred circuit.
>
>
well i heard darrel johnson saying that it is better to use a LDR instead of
photodiodes because they could see bright objects(like the thing in white or
hand) other than light....so is this possible with photodiodes and if i am
using a LDR should i use it in series with a diode?thanks a lot wilf

______________________________________________________



6123 Fri, 17 Sep 1999 13:51:08 -0500 [alt-beam] Re: power_smart_head fest beam@sgiblab.sgi.com Scott Burns Success! I double checked all components--they were all correct. I tried
the new resistor values you suggested--no improvement. Then I read about
the high frequency problem and strapped a big honkin' capacitor across my
power supply and it worked! I have one of those Elenco "Precision" quad
power supplies. I can't see any ripple on my scope, but maybe there's a
high frequency noise in there somewhere. I _am_ using V1 of the PSH, aren't
I? Should it be so sensitive?

Thanks for all your help!

Scott

At 08:51 AM 9/17/99 -0700, you wrote:
>Well.....
>
>I have protoboarded the ps head exactly the way it is shown on your webpage
>and it works perfectly for me. I have tried a variety of chips and
>component values and it just keeps on working. It certainly is more
>sensitive with photodiodes and more active with the 1K resistors removed but
>LDRs with or without 1K resistors work fine too. Are you certain of the
>component values? Capacitors can have a wide tolerance but even so that
>should not produce the problem you show. If the LDRs are very low value (100
>ohm in moderate light) the 1K resistors may interfere. If the 1K resistors
>are 10K that would also explain the behaviour in bright light. One other
>experiment is to swap the 10M and 5.6M resistors: note the difference in
>behaviour in low light and when the LDRs are balanced. The best "tuning" of
>the circuit ended up with the 5.6M resistor changed to 10M and the 10M
>resistor changed to 9.1M. The absolute values are less important than the
>ratios and the original circuit works quite well but is somewhat
>conservative (and snoozy) compared to the fine tuned values.
>
>One more comment: the PS head V1 is robust and stable and the high frequency
>problem I referred to earlier is easily controlled with a 0.1 uf cap across
>the motor. The PS head V2 and V3 circuits require critical adjustments and
>are not recommended for the faint of heart. Since the objective of the later
>versions was to control high frequencies, the much simpler V1 with a cap
>across the motor is the preferred circuit.
>
>
>
> Wilf Rigter mailto:wilf.rigter@powertech.bc.ca
> tel: (604)590-7493
> fax: (604)590-3411
>
> > -----Original Message-----
> > From: Scott Burns [SMTP:s-burns@uiuc.edu]
> > Sent: Thursday, September 16, 1999 9:16 AM
> > To: beam@sgiblab.sgi.com
> > Subject: RE: power_smart_head fest
> >
> > At 06:12 PM 9/10/99 -0700, you wrote:
> > >Hello Scott,
> > >
> > >Tell us more: what components? which schematic? what motor? matched LDRs?
> > >
> > >best regards
> > >
> > > Wilf Rigter mailto:wilf.rigter@powertech.bc.ca
> > >
> >
> > OK, I've described it in detail (including scope readings) at
> >
> > http://www.designbyalgorithm.com/circuit.htm
> >
> > > > -----Original Message-----
> > > > From: Scott Burns [SMTP:s-burns@uiuc.edu]
> > > > Sent: Friday, September 10, 1999 7:05 AM
> > > > To: beam@sgiblab.sgi.com
> > > > Subject: Re: power_smart_head fest
> > > >
> > > > Dear Wilf:
> > > >
> > > > The virtual beam workshop sounds great. I tried building the PSH and
> > was
> > > > able to get the square waves to the motor to change duty cycle with
> > > > changes
> > > > in relative LDR illumination, but they were always in phase. The motor
> > > > never saw a voltage differential across it. I'm anxious to figure out
> > what
> > > >
> > > > I did wrong.
> > > >
> > > > Regards, Scott
> > > >
> > > >
> >
> > ------------------------------------------
> > Prof. Scott A. Burns
> > Dept of General Engineering and Civil Engineering
> > University of Illinois at Urbana-Champaign
> > 104 S. Mathews, Urbana, IL 61801
> > Phone 217/333-1618, FAX 217/244-5705

------------------------------------------
Prof. Scott A. Burns
Dept of General Engineering and Civil Engineering
University of Illinois at Urbana-Champaign
104 S. Mathews, Urbana, IL 61801
Phone 217/333-1618, FAX 217/244-5705



6124 Fri, 17 Sep 1999 15:22:42 EDT [alt-beam] Re: BG Micro Motors beam@sgiblab.sgi.com Gadagada@aol.com In a message dated 9/16/99 10:49:59 PM Eastern Daylight Time,
dilbertpete@hotmail.com writes:

<< Hello Everyone,
I am looking for a source of BG Micro Motors for a microcore. Does anyone
know where I can find them??

Thank you very much
-Pete >>


Ah, the famous BG Micro Motor source conundrum. Your only hope is to find
someone on the list who has some and shamelessly bribe them (your soul might
be a fair trade for a few). Or, at the risk of death by firing squad, you
could email Nihon (I think that's it) and tell them you are a defense
contractor looking to buy massive quantities of 30 rpm, 3v, very efficient DC
gearhead motors and would like some samples. Either way, good luck.



Gary



6125 Fri, 17 Sep 99 13:51:31 -0600 [alt-beam] BEAM news site Ian Bernstein Hi
I'm getting back into my web site and would like to keep up the news with
maybe a daily update but it would help greatly if I had one or two people
helping me. You would be given full credit (at the top it would say - by
Your Name - or something like that). I was thinking maybe I could do 4
days of the week and you could do the other 3 and if we had more people
it could be 3 - 2 - 2. Also we could maybe do a bi-weekly update so it
would be 1 - 1. All you would have to do is send me an e-mail with the
news and links and I'll do the html web stuff and upload it. Let me know
if your interested. Happy BEAMing

Laterz


*-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-*
Ian Bernstein "aka - Synet" The Master Builder

E-Mail - Ian@beam-online.com
BEAM Online - http://www.beam-online.com
Quote - "Into everyone's life, a little rain must fall, but this
is
ridiculous."
- Noah

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