Timer problem with Parallel port monitoring

[amcg...@gmail.com]

Hey everyone,
I'm very much so a newbie at electronics, but figured I'd try and tackle a problem for my scout group: making a pinewood car timer.

I found this schematic online that uses optical transmitters:
http://www.hmpg.net/pinewood/GenericPinewoodTimerSchematic.pdf

I have hooked everything up as seen in the schematic to the best of my ability... I have hooked up the parallel port grounds (Pins 18-25) also to the negative row at the bottom of my breadboard, so all the grounds are on the same line (I couldn't figure out how else to do that).

Here's my problem: Using parmon to monitor the parallel port, when I hit any of the sensors (say the start gate for example), it changes the status on all the pins that are hooked up.

Example:
Pins 10,11,12,13, and 15 all read "1". I trigger the start gate switch (hooked up to pin 15). Now ALL of my pins (10,11,12,13, and 15) all toggle over to "0". Similar thing happens if I hit just ONE photoelectric diode with a flashlight, ALL trip to 0, not just the one pin that that diode is hooked to.

I've written my matlab code to poll everything and run the race, but since I can't differentiate which sensor is getting twigged, I can't determine which sensor came across first...

Any help/suggestions would be fantastic.

Thanks in advance,
Andrew

[John Larkin]

Make sure all the grounds are connected. Then check the 5 volt supply, with a
voltmeter maybe, and make sure it stays 5 volts.


--

John Larkin Highland Technology Inc
www.highlandtechnology.com jlarkin at highlandtechnology dot com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom timing and laser controllers
Photonics and fiberoptic TTL data links
VME analog, thermocouple, LVDT, synchro, tachometer
Multichannel arbitrary waveform generators

[Daniel Pitts]

On 5/13/13 8:10 AM, John Larkin wrote:
> On Mon, 13 May 2013 06:54:03 -0700 (PDT), amcg...@gmail.com wrote:
>
>> Hey everyone,
>> I'm very much so a newbie at electronics, but figured I'd try and tackle a problem for my scout group: making a pinewood car timer.
>>
>> I found this schematic online that uses optical transmitters:
>> http://www.hmpg.net/pinewood/GenericPinewoodTimerSchematic.pdf
>>
>> I have hooked everything up as seen in the schematic to the best of my ability... I have hooked up the parallel port grounds (Pins 18-25) also to the negative row at the bottom of my breadboard, so all the grounds are on the same line (I couldn't figure out how else to do that).
>>
>> Here's my problem: Using parmon to monitor the parallel port, when I hit any of the sensors (say the start gate for example), it changes the status on all the pins that are hooked up.
>>
>> Example:
>> Pins 10,11,12,13, and 15 all read "1". I trigger the start gate switch (hooked up to pin 15). Now ALL of my pins (10,11,12,13, and 15) all toggle over to "0". Similar thing happens if I hit just ONE photoelectric diode with a flashlight, ALL trip to 0, not just the one pin that that diode is hooked to.
>>
>> I've written my matlab code to poll everything and run the race, but since I can't differentiate which sensor is getting twigged, I can't determine which sensor came across first...
>>
>> Any help/suggestions would be fantastic.
>>
>> Thanks in advance,
>> Andrew
>
> Make sure all the grounds are connected. Then check the 5 volt supply, with a
> voltmeter maybe, and make sure it stays 5 volts.
>
>

When you toggle the "start gate" switch, only pin 15 should change from
high to low (voltage, I don't know whether that means 0 or 1).

If more than that switches, check the voltage levels from ground to the
rest of the pins. It could be that your "power supply" just can't handle
the load.

Make sure you're using 10kΩ resistors (brown black orange). Test them
with an ohm meter (removing them from the circuit first).

Make sure your not inadvertently shorting the signal lines some how.

Try disconnecting all the phototransistors. With-out them in the
circuits, you should read all high-level except for the start-level
switch. If that *isn't* the case, start removing all the other line
connections until it is the case.

Perhaps you could upload a photo of your protoboard somewhere for us to
look at. Sometimes you think you've wired it one way, but it is actually
wired a different way.

Anyway, I hope my suggestions help you. I'm somewhat new to this myself.

Good luck,
Daniel.

[amcg...@gmail.com]

>
>
>
> Make sure all the grounds are connected. Then check the 5 volt supply, with a
>
> voltmeter maybe, and make sure it stays 5 volts.
>

John:
Thanks so much for your response. I will check this out, hopefully I can squeeze it in over lunch.

[Tim Wescott]

The two suggestions that you've gotten -- to check the +5V supply and to
check all grounds -- are both things that I'd recommend.

Checking the voltages at pins 10-13, pin 15, and your +5V line when you
exercise the start gate and the photodetectors should also be
informative. If the circuit is working correctly then the voltage on any
one of the five sense lines should be independent of the rest, and the
+5V line should not be affected.

If you _do_ see cross-talk on the data lines but not the +5V, then try it
again with the thing disconnected from the 'puter. In general you want
to chop the problem up into little bits and solve (or verify) those bits
independently.

When you're all done, check that the thing actually times accurately
under whatever OS you're using -- both Windoze and Linux aren't real
time, and the more we use nifty graphics and such the less real time they
get. If the software you intend to use has as decently written port
driver and makes wise use of multimedia timing constructs then it should
do a pretty good job. If not -- maybe not.

(Or, if you're _really_ techie, use a 4-channel digital scope connected
to the four lane sensors, with the start gate connected to the trigger.
There's nothing like throwing $5000 worth of equipment at a $10 problem
to prove that you're a techno-nerd).

--
My liberal friends think I'm a conservative kook.
My conservative friends think I'm a liberal kook.
Why am I not happy that they have found common ground?

Tim Wescott, Communications, Control, Circuits & Software
http://www.wescottdesign.com

[amcg...@gmail.com]

EVERYONE:
Thanks so much for your input. I thought I'd have time on my lunch break to test some things but couldn't squeeze it in. I'm going to go through these tests this evening and try to isolate/debug it.

Thanks everyone for the help!

Cheers,
Andrew

[P E Schoen]

wrote in message
news:02445a1d-dca3-4feb...@googlegroups.com...

> EVERYONE:
> Thanks so much for your input. I thought I'd have time on my lunch break
> to test some things but couldn't squeeze it in. I'm going to go through
> these tests this evening and try to isolate/debug it.

> Thanks everyone for the help!

I was not familiar with parmon so I looked into it and it seems like a
useful program. I also found many other helpful tutorials and applications.
Interfacing to the parallel port was pretty easy with MSDOS and early
computers as were standard when I developed some products in the early
1990s, but after Win98 and the ubiquitous USB port, the LPT port vanished
and I had to redesign my hardware and software. Here are some links that may
help:

http://www.geekhideout.com/parmon.shtml (updated version with bug fix)
http://www.youtube.com/watch?v=91EKTPyfg0U
http://stadi.hu/sw/lptdebug_en.html
http://www.youtube.com/watch?v=FHCvrn9B6W0
http://www.youtube.com/watch?v=UBq4CGFsI5Q
http://www.youtube.com/watch?v=btpE8-2xKFw
http://www.amazon.com/Programming-Parallel-Port-Interfacing-Acquisition/dp/0879305134
http://www.lvr.com/parport.htm (Jan Axelson)
http://logix4u.net/parallel-port/16-inpout32dll-for-windows-982000ntxp
(inpout32.dll)
http://msdn.microsoft.com/en-us/library/windows/hardware/ff544392(v=vs.85).aspx

Good luck with your project!

Paul

[Jasen Betts]

"GND" at the bottom if the diagram should be connected directly to "GND"
on the parallel port and to nothing else.

+5V should always measure about 5V to gnd (parport pin 25)
any voltage from (3.5 to 5.5V) should be ok.


the device can probably be powered from pins 1-5 of the parallel port
instead of from an external supply. to do this: to set those pins to
output and high. Then disconnect the top end of each resistor and
reconnect it to diffetent parport pin.

--
⚂⚃ 100% natural

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[tuinkabouter]

The RS-232 standard defines the voltage levels that correspond to
logical one and logical zero levels for the data transmission and the
control signal lines. Valid signals are either in the range of +3 to +15
volts or the range -3 to -15 volts with respect to the ground/common pin;
consequently, the range between -3 to +3 volts is not a valid RS-232 level.

see https://en.wikipedia.org/wiki/RS-232#Voltage_levels

Some PC builders cut corners and then it may work.
So try another PC or redesign the schematic.

[P E Schoen]

"tuinkabouter" wrote in message news:kmu4ih$v6e$1...@dont-email.me...

> The RS-232 standard defines the voltage levels that correspond to logical
> one and logical zero levels for the data transmission and the control
> signal lines. Valid signals are either in the range of +3 to +15 volts or
> the range -3 to -15 volts with respect to the ground/common pin;
> consequently, the range between -3 to +3 volts is not a valid RS-232
> level.

> see https://en.wikipedia.org/wiki/RS-232#Voltage_levels

> Some PC builders cut corners and then it may work.
> So try another PC or redesign the schematic.

The OP is using the Centronics parallel port and not the RS-232 serial port.
Older computers used a 25 pin Dsub connector for both, but the serial port
was male while the parallel port has always been female. The early parallel
ports used an 8255 PIO which could be reconfigured by writing to the control
port address, but in later machines it was usually incorporated into
proprietary chips on the motherboard (or on plug-in ISA or PCI cards).

There were some improvements (enhancements) to the parallel port such as
EPP, which I think was faster and designed for bidirectional data transfer.
But it had to be compatible with old versions of software and hardware so
there is usually a BIOS option for SPP or EPP. AFAIK all of them use TTL or
CMOS logic levels of nominally 0 and 5 VDC with transition at about 0.7V.

I have also found that some parallel ports work much better if pull-up
resistors of 4.7k or so are added.

Paul