Need help modifying treadmill.

[eng1]

It seems like the diode is not connected as showed in the schematic. If so, the relay will never be ON and the diode will get hot soon.

 

[Mipoleon]

The Radioshack part number is 276-1723 and the other part, I believe is, number is 555CN. I dont have it in front of me at the moment but I belive those are correct.

 

[Mipoleon]

It seems like the diode is not connected as showed in the schematic. If so, the relay will never be ON and the diode will get hot soon.

I got the side of the diode with the black line on it soldered to Pin3 and the other end soldered to the ground. My picture is not very clear there with the wire going across the soldering. If that is incorrect please let me know what is correct.

 

[eng1]

It's OK then

 

[Mipoleon]

What is the complete part number of your 555?

Just got home and looked. It is a 555CN.

 

[AllVol]

I must have something wrong but am unable to determine what it is.

I may be reading the photos wrong, and if I am, sorry for the confusion, but the two resistors at line 15(16) and 20?? on the board are both shown as being connected to ground. They should be connected to the positive rail. They are what keeps the trigger high until it receives a negative-going pulse by the magnetic switch going to ground.

 

[Roff]

I may be reading the photos wrong, and if I am, sorry for the confusion, but the two resistors at line 15(16) and 20?? on the board are both shown as being connected to ground. They should be connected to the positive rail. They are what keeps the trigger high until it receives a negative-going pulse by the magnetic switch going to ground.

You appear to be assuming the board is flipped top to bottom. I believe it is flipped left to right. I do appreciate any help you can offer. I'm about to conclude the 555 is bad. I usually use sockets for this reason.

 

[AllVol]

You appear to be assuming the board is flipped top to bottom.

Radio Shack's little boards use edge numbers to assist in placement of components (marketing gimmick, I think). Notice that on the component side, the lines are consecutively numbered 1 though 30. On the flip side, they are shown by five's.

If you look carefully, it appears the "top" of those two resistors in the trigger lead (at positions 15 or 16 and about 20-something) are soldered to his ground bus. This would sure account for the problem.

A 555 in mono when triggered will stay high until the trigger returns to high despite the timing. It's kinda like Tennessee's basketball team at tournament time - one and done.

A multimeter between pin 3 and ground should show a continuous positive voltage right from power-up if I am correct.

 

[Roff]

Radio Shack's little boards use edge numbers to assist in placement of components (marketing gimmick, I think). Notice that on the component side, the lines are consecutively numbered 1 though 30. On the flip side, they are shown by five's.

If you look carefully, it appears the "top" of those two resistors in the trigger lead (at positions 15 or 16 and about 20-something) are soldered to his ground bus. This would sure account for the problem.

A 555 in mono when triggered will stay high until the trigger returns to high despite the timing. It's kinda like Tennessee's basketball team at tournament time - one and done.

A multimeter between pin 3 and ground should show a continuous positive voltage right from power-up if I am correct.

It's clear from the numbers that the board is flipped left to right. The resistors in the trigger circuit are connected to the bus at the bottom (in the picture) of the board, which is +9V.

 

[Mipoleon]

Board is flipped left to right in the picture.

Maybe this will help. I flipped the pictures around to make more sense and labeled Pin 1.

 

[Mipoleon]

If we conclude that the 555 is bad is it possible that anything else could be bad as well? As far as I can tell it should work. Is it also possible that they may not be enough of whatever it takes to trigger the relay coil going to the coil? Sometimes there seems to be electricity going to the coil but the coil doesn't trigger.

 

[Roff]

If we conclude that the 555 is bad is it possible that anything else could be bad as well? As far as I can tell it should work. Is it also possible that they may not be enough of whatever it takes to trigger the relay coil going to the coil? Sometimes there seems to be electricity going to the coil but the coil doesn't trigger.

With a fresh 9V battery into an 500 ohm load (the relay coil), your output high voltage will be about 7.6V. The relay specs say it needs at least 7 volts. Nine volt batteries are pretty wimpy. Measure you battery voltage when the relay coil is energized. You might be better off with a beefier battery and/or a 6V relay. Your battery is not going to last long if the relay is always energized.
A better solution than a relay would probably be an optocoupler. If you use a CMOS 555 and an efficient optocoupler (high current transfer ratio), you could probably reduce your battery current to a couple of milliamps.

 

[eng1]

Have you tried to trigger the NE555 "manually"? You may add a 1000 ohms resistor and connect it to ground for a moment. C3 discharges through Rb quickly, generating a negative spike.

 

[Mipoleon]

Have you tried to trigger the NE555 "manually"?

Im not sure that I know how to do that.

Is there any place online that I might be able to just buy one of these devices? At this point it seems like I am just wasting my time and money.

 

[Mipoleon]

Or maybe there is another simpler way to do it. Maybe a switch that can detect the wheel motion or a circuit that I can mechanically attach to the wheel that will stay closed as long as it is rotating?

 

[Roff]

Or maybe there is another simpler way to do it. Maybe a switch that can detect the wheel motion or a circuit that I can mechanically attach to the wheel that will stay closed as long as it is rotating?

You might try this. You might have to change the resistor value.