Kids Bike Timer circuit not working, Why?

T

Tristar

Guest
Kids Bike Timer circuit not working, Why?

OK, I checked and double checked all my solder joints and can't find
anything out of place or poorly soldered. I ran a check on the 555
timers before adding them to the board. All IC's are soldered directly to
the board. This is a two sided board and I found it about impossible to
solder a IC socket on both sides of the board.

Here's what I'm doing and here's what is happening/not happening.

Depress SW2 once, LED lights up. (this is an indication that the missing
pulse detector is working) As long as SW2 is pressed once every few
seconds the LED will remain lit. (SW2 will later be replaced by a reed
switch triggered by a magnet attached to the wheel of the child's
exercise bike.)

OK, I press SW2 and then SW1 (SW1 should start the countdown) and then
keep pressing SW2 every few seconds to keep it active.

What is supposed to happen at 30 seconds is that contacts at CN1 are to
close triggering a small prerecorded voice chip announce the successful
completion of 30 seconds of pedaling. 30 seconds later CN2 should go off
etc..

I can successfully set the length of time the missing pulse detector will
tolerate with the pot at R12.

Nothing else seems to happen. I've got power and ground to the IC's. I
did notice the two 555's get warm but not real hot.

Any ideas? I'm not sure where to start troubleshooting this.

I'm posted a capture of the board and the schematic John Fields and the
rest of you have helped me put together
at alt.binaries.schematics.electronic

Thanks for your patience here!

Lawrence
alt.binaries.schematics.electronic
 
On Wed, 24 Aug 2005 16:00:12 GMT, Tristar <admin@nospam.com> wrote:

Kids Bike Timer circuit not working, Why?

OK, I checked and double checked all my solder joints and can't find
anything out of place or poorly soldered. I ran a check on the 555
timers before adding them to the board. All IC's are soldered directly to
the board. This is a two sided board and I found it about impossible to
solder a IC socket on both sides of the board.

Here's what I'm doing and here's what is happening/not happening.

Depress SW2 once, LED lights up. (this is an indication that the missing
pulse detector is working) As long as SW2 is pressed once every few
seconds the LED will remain lit. (SW2 will later be replaced by a reed
switch triggered by a magnet attached to the wheel of the child's
exercise bike.)

OK, I press SW2 and then SW1 (SW1 should start the countdown) and then
keep pressing SW2 every few seconds to keep it active.

What is supposed to happen at 30 seconds is that contacts at CN1 are to
close triggering a small prerecorded voice chip announce the successful
completion of 30 seconds of pedaling. 30 seconds later CN2 should go off
etc..

I can successfully set the length of time the missing pulse detector will
tolerate with the pot at R12.

Nothing else seems to happen. I've got power and ground to the IC's. I
did notice the two 555's get warm but not real hot.
Click to expand...
---
Those are supposed to be 7555's (CMOS 555's) and they should be
stone cold.
---


Any ideas? I'm not sure where to start troubleshooting this.

I'm posted a capture of the board and the schematic John Fields and the
rest of you have helped me put together
at alt.binaries.schematics.electronic
Click to expand...
---
What kind of test equipment do you have?

--
John Fields
Professional Circuit Designer
 
The two 555's are cmos IC's. They are both mouser part number 511-TS555CN.

I'm running 6 VDC as input voltage from a gel cell battery.

Lawrence

In article <17apg1lf7a3dstals7bcnnua9v9mdpgrgl@4ax.com>,
jfields@austininstruments.com says...
On Wed, 24 Aug 2005 16:00:12 GMT, Tristar <admin@nospam.com> wrote:

Kids Bike Timer circuit not working, Why?

OK, I checked and double checked all my solder joints and can't find
anything out of place or poorly soldered. I ran a check on the 555
timers before adding them to the board. All IC's are soldered directly to
the board. This is a two sided board and I found it about impossible to
solder a IC socket on both sides of the board.

Here's what I'm doing and here's what is happening/not happening.

Depress SW2 once, LED lights up. (this is an indication that the missing
pulse detector is working) As long as SW2 is pressed once every few
seconds the LED will remain lit. (SW2 will later be replaced by a reed
switch triggered by a magnet attached to the wheel of the child's
exercise bike.)

OK, I press SW2 and then SW1 (SW1 should start the countdown) and then
keep pressing SW2 every few seconds to keep it active.

What is supposed to happen at 30 seconds is that contacts at CN1 are to
close triggering a small prerecorded voice chip announce the successful
completion of 30 seconds of pedaling. 30 seconds later CN2 should go off
etc..

I can successfully set the length of time the missing pulse detector will
tolerate with the pot at R12.

Nothing else seems to happen. I've got power and ground to the IC's. I
did notice the two 555's get warm but not real hot.

---
Those are supposed to be 7555's (CMOS 555's) and they should be
stone cold.
---


Any ideas? I'm not sure where to start troubleshooting this.

I'm posted a capture of the board and the schematic John Fields and the
rest of you have helped me put together
at alt.binaries.schematics.electronic

---
What kind of test equipment do you have?

--
John Fields
Professional Circuit Designer
Click to expand...
 
Sorry, no scope. Just a pair of multimeters, digital and analog.


Lawrence
 
On Thu, 25 Aug 2005 13:35:46 GMT, Tristar <admin@nospam.com> wrote:

Sorry, no scope. Just a pair of multimeters, digital and analog.
Click to expand...
---
You need to leave a little bit of the message you replied to in your
reply so we can see what you're replying to.

OK, first we need to find out why the 7555's are running warm.

Set all the pots at their midpoints and measure all the voltages on
the 7555's, relative to ground. With a 6V supply you should get, on
both chips:

PIN | VOLTAGE
---------------
1 0
2 6
3 0
4 <0.4
5 4
6 6
7 6
8 6

The voltage on pin 4 will be greater than 0.4V, and that's a design
error, but it won't affect whether the chips run hot or not, so
we'll deal with that later. Also, the RC network on U1 has a long
time constant, so if you measure the voltage on pins 2 and 6
(they're supposed to be in parallel) soon after you power up the
circuit, the voltage may not have risen to 6V by the time you get
there, and if it hasn't you should see it rising slowly. Be sure to
use your digital meter to make the measurement, since the current
source for the cap is the 2 meg pot cranked down to 1 meg and if you
use your analog meter (which I assume has an input impedance of
something like 20000 ohms per volt) It'll just swamp the capacitor
and cause the voltage to start falling as soon as you put the probe
on pin2.

Hmmm... It just occurred to me that the reason for the 7555's
running warm might be that if you haven't adjusted the pots to half
scale then they could be sitting anywhere, and if they're sitting at
minimum resistance then current will just be _pouring_ into the poor
little 7555's. Ouch!!! You might want to adjust the pots for
half-scale and try to run the thing again. It might just work if the
7555's haven't been toasted.

Post back with what you find.

--
John Fields
Professional Circuit Designer
 
In article <1s9sg1lu4e101158sjqgrcquip6rqsck12@4ax.com>,
jfields@austininstruments.com says...
OK, here's my readings.

PIN | VOLTAGE
---------------
1 0
2 6
3 0
4 .647
5 3.0 mv
6 3.0 mv
7 6
8 6
Click to expand...

They may have been getting hot due to the position of the pots. with the
pots centered they seem to stay cool.

Lawrence


On Thu, 25 Aug 2005 13:35:46 GMT, Tristar <admin@nospam.com> wrote:

Sorry, no scope. Just a pair of multimeters, digital and analog.

---
You need to leave a little bit of the message you replied to in your
reply so we can see what you're replying to.

OK, first we need to find out why the 7555's are running warm.

Set all the pots at their midpoints and measure all the voltages on
the 7555's, relative to ground. With a 6V supply you should get, on
both chips:

PIN | VOLTAGE
---------------
1 0
2 6
3 0
4 <0.4
5 4
6 6
7 6
8 6

The voltage on pin 4 will be greater than 0.4V, and that's a design
error, but it won't affect whether the chips run hot or not, so
we'll deal with that later. Also, the RC network on U1 has a long
time constant, so if you measure the voltage on pins 2 and 6
(they're supposed to be in parallel) soon after you power up the
circuit, the voltage may not have risen to 6V by the time you get
there, and if it hasn't you should see it rising slowly. Be sure to
use your digital meter to make the measurement, since the current
source for the cap is the 2 meg pot cranked down to 1 meg and if you
use your analog meter (which I assume has an input impedance of
something like 20000 ohms per volt) It'll just swamp the capacitor
and cause the voltage to start falling as soon as you put the probe
on pin2.

Hmmm... It just occurred to me that the reason for the 7555's
running warm might be that if you haven't adjusted the pots to half
scale then they could be sitting anywhere, and if they're sitting at
minimum resistance then current will just be _pouring_ into the poor
little 7555's. Ouch!!! You might want to adjust the pots for
half-scale and try to run the thing again. It might just work if the
7555's haven't been toasted.

Post back with what you find.

--
John Fields
Professional Circuit Designer
Click to expand...
 
On Fri, 26 Aug 2005 13:00:11 GMT, Tristar <admin@nospam.com> wrote:

In article <1s9sg1lu4e101158sjqgrcquip6rqsck12@4ax.com>,
jfields@austininstruments.com says...


OK, here's my readings.

PIN | VOLTAGE
---------------
1 0
2 6
3 0
4 .647
5 3.0 mv
6 3.0 mv
7 6
8 6


They may have been getting hot due to the position of the pots. with the
pots centered they seem to stay cool.
Click to expand...
---
That's what it was, then.

There's still a problem, though. Pins 6 and 7 should be at 3mV and
pin 5 should be at about 4V. It looks like pins 6 and 7 are
parallelled in your board capture jpeg so I suspect you made a
transcription error. Why don't you go check again and see what you
get, since everything else looks OK . The 6V on pins 6 and 7 that I
put on my chart was wrong. I forgot that with the output (pin 3)
low the discharge MOSFET is turned on so it can discharge the cap,
so what you were reading (3mV) is good.

Post back with what you find, and if everything is OK we'll go on to
the next step.

--
John Fields
Professional Circuit Designer
 
John, you are right, Transcription error.

PIN | VOLTAGE
---------------
1 0
2 6
3 0
4 4
5 3.0 mv
6 3.0 mv
7 6
8 6
Click to expand...
This is what I should have posted.



Lawrence
In article <v6aug1trr1ahd3bssie876g6m22tiet687@4ax.com>,
jfields@austininstruments.com says...
On Fri, 26 Aug 2005 13:00:11 GMT, Tristar <admin@nospam.com> wrote:

In article <1s9sg1lu4e101158sjqgrcquip6rqsck12@4ax.com>,
jfields@austininstruments.com says...


OK, here's my readings.

PIN | VOLTAGE
---------------
1 0
2 6
3 0
4 .647
5 3.0 mv
6 3.0 mv
7 6
8 6


They may have been getting hot due to the position of the pots. with the
pots centered they seem to stay cool.

---
That's what it was, then.

There's still a problem, though. Pins 6 and 7 should be at 3mV and
pin 5 should be at about 4V. It looks like pins 6 and 7 are
parallelled in your board capture jpeg so I suspect you made a
transcription error. Why don't you go check again and see what you
get, since everything else looks OK . The 6V on pins 6 and 7 that I
put on my chart was wrong. I forgot that with the output (pin 3)
low the discharge MOSFET is turned on so it can discharge the cap,
so what you were reading (3mV) is good.

Post back with what you find, and if everything is OK we'll go on to
the next step.

--
John Fields
Professional Circuit Designer
Click to expand...
 
On Fri, 26 Aug 2005 20:13:10 GMT, Tristar <admin@nospam.com> wrote:

John, you are right, Transcription error.

PIN | VOLTAGE
---------------
1 0
2 6
3 0
4 4
5 3.0 mv
6 3.0 mv
7 6
8 6


This is what I should have posted.
Click to expand...
---
I'm getting confused.

From your last post, if it was a transcription error, this is what
you should have:

PIN | VOLTAGE
---------------
1 0
2 6
3 0
4 ~ 0.6
5 4
6 3.0 mv
7 3.0 mv
8 6

No need to post another chart, if that's what you have just say so
and we can continue.

And _please_ bottom post so we can keep track of the chronology.


--
John Fields
Professional Circuit Designer
 
Sorry, Yes, I have the values you charted.

In article <rh1vg1dfqda51pe71c8647u2cbeiskh929@4ax.com>,
jfields@austininstruments.com says...
On Fri, 26 Aug 2005 20:13:10 GMT, Tristar <admin@nospam.com> wrote:

John, you are right, Transcription error.

PIN | VOLTAGE
---------------
1 0
2 6
3 0
4 4
5 3.0 mv
6 3.0 mv
7 6
8 6


This is what I should have posted.

---
I'm getting confused.

From your last post, if it was a transcription error, this is what
you should have:

PIN | VOLTAGE
---------------
1 0
2 6
3 0
4 ~ 0.6
5 4
6 3.0 mv
7 3.0 mv
8 6

No need to post another chart, if that's what you have just say so
and we can continue.

And _please_ bottom post so we can keep track of the chronology.


--
John Fields
Professional Circuit Designer
Click to expand...
 
On Fri, 26 Aug 2005 20:13:10 GMT, Tristar <admin@nospam.com> wrote:

John, you are right, Transcription error.
Click to expand...
---
Please bottom post.

OK. Since U1A seems to be OK, The next thing to do is to check out
U5A and the wiring to U1 and U2. First, with power down, make sure
you have continuity between U1-4 and all the other points shown
connected to it on the schematic. Then, with R12 adjusted to
mid-scale, apply power, connect your voltmeter to U1-4 and press and
release S2. The LED should light and the voltmeter reading should
go high immediately (rise to 6V) and stay there for about seven
seconds, then the LED should go off and the reading should go low
(fall to ~0V (0.6V is OK)) and stay there.

It that works, the next step is to test the timer.

Connect your voltmeter to U1-3 and press S2. The LED should come on
and the voltmeter should read 0V. While making sure that The LED
stays lit by pressing S2 every five seconds or so, press and release
S1. U1-3 should go high immediately and stay there as long as you
keep pressing and releasing S2. If it does, after 20 seconds or so,
stop pressing and releasing S2. The LED should go out in about
seven seconds and when that happens U1-3 should go low and stay low.

Try all that and please bottom-post pack with what you find.

P.S... If you want to make things a little easier, you could build
an astable multivibrator with the other 7555 you've been playing
with and connect its output to the junction of R11 and S2. That
would simulate the button pressings and relieve you of the task of
having to continuously press and release S2 while doing other things
at the same time. It's a very easy circuit, and you can find it in
Figure 1-A of the 7555 data sheet, located at:

http://pdfserv.maxim-ic.com/en/ds/ICM7555-ICM7556.pdf

Use a 1 megohm resistor and a 1ľF capacitor an you'll get about 1.5s
out which will be fine.


--
John Fields
Professional Circuit Designer
 
Tristar wrote:

You may have missed my reply elsewhere. I think you have a
problem where the output transistors do not appear to have a
+ source connected to the collectors, if I recall the post.

Ed
 
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