beam : Message: Re: [beam] Re: BBPV Foolery

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BBPV Foolery

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Message #38523 of 60865 |

Re: [beam] Re: BBPV Foolery

Hi Wolfgang,

I always socket my chips just in case of such "fingertrouble".

I suggest you build and test the BBPV on a protoboard to prove that the components in this simple circuit all work together and drive the motors hither and yonder.

The BBPV is a little vulnerable to damage if a motor with too low resistance is connected to the first driver stage. That can cause the logic level on the second driver paralleled inputs (connected to first driver outputs) to be near the switching threshold. That can cause up to 200ma to flow through the second stage output stage and the circuit can selfdestruct from internal thermal overload.

A slightly different design uses two inverters in series to process the photo input stage and uses the first and second inverter outputs to drive the respective parallel inputs of 2 groups of 3 inverters used as motordrivers. A small layout drawing is attached.

The addition of the cap changes behaviour in different light conditions like the BeamANT.

wilf

----- Original Message -----

From: J Wolfgang Goerlich

To: beam@yahoogroups.com

Sent: Saturday, August 16, 2003 5:25 PM

Subject: [beam] Re: BBPV Foolery

Thank you for that, Wilf. It appears I have a bad chip. Would this problem be related to when we melted the photodiodes? Or is it more likely to be heat related? I ask because I am debating whether or not to buy a DIP socket. J Wolfgang Goerlich > Check: connect the midpoint of the two series PDs of the BBPV > through a small (100ohm) resistor to 240 pin 20 and one motor > should turn. Then connect the resistor to 240 pin 10 and the other > motor should turn. If OK the PDs are the problem. If not OK the > chip is the problem. Post Script: > wilfred Adding a few more letters between us, eh? :)

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Sun Aug 17, 2003 2:31 am

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"wilf rigter" <wrigter@...>

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Message #38523 of 60865 |

Expand Messages	Author	Sort by Date
Foolery I hate to say it, but we are still having problems building a robot using the Bare Bones Photovore circuit. The only difference is that the original...	J Wolfgang Goerlich jwgoerlich_us	Aug 16, 2003 7:37 pm
Hello Wolfgang, Check: connect the midpoint of the two series PDs of the BBPV through a small (100ohm) resistor to 240 pin 20 and one motor should turn. Then ...	Wilf Rigter wilf_nv	Aug 16, 2003 7:57 pm
Thank you for that, Wilf. It appears I have a bad chip. Would this problem be related to when we melted the photodiodes? Or is it more likely to be heat...	J Wolfgang Goerlich jwgoerlich_us	Aug 17, 2003 12:25 am
What is the best way to set up photodiodes for a photovore? I've tried lot of things, but one way i did it made the bot act perfectly, but then he was...	Adam morrows_end	Aug 17, 2003 2:10 am
Hi Wolfgang, I always socket my chips just in case of such "fingertrouble". I suggest you build and test the BBPV on a protoboard to prove that the components...	wilf rigter wilf_nv	Aug 17, 2003 2:30 am
... Ok, I will use a socket. ... Makes sense. I am assuming that I can build this on a breadboard instead of protoboard to achieve the same objective. ... ...	J Wolfgang Goerlich jwgoerlich_us	Aug 17, 2003 7:45 am
Hello Wilf, I see you used the 74HC240 in the BBPV2 circuit, while Solarbotics used the 74AC240 in the original BBPV. Unfortunately, I am out of HCs, and I see...	J Wolfgang Goerlich jwgoerlich_us	Aug 17, 2003 4:22 pm
Sorry, I meant the generic HC/AC240 chip. The 74AC240 is the preferred type with higher available output current and a relatively symmetrical switching...	Wilf Rigter wilf_nv	Aug 17, 2003 7:41 pm

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