The BS2p24

Discovery

I built a plug-in breadboard using a BS2e to control 120 vac 60 Hz solenoids via electronic switches in accordance with specific hours and minutes read from a real-time clock. This controller worked perfectly...then I added a BS2p24 to gather one-wire measurements that were processed and the results sent to the BS2e for controlling the solenoids. What happened was the BS2p24 would stop running its program whenever a solenoid would activate and deactivate.

If you have encountered this problem with the BS2p24 and have a verified solution...I would appreciate knowing what needs to be done to prevent the problem. I suspect EMI pulses are the culprit but have not verified the mechanism.

Sincerely,

Discovery

AwesomeCronk

Are the two stamps sharing a power supply? I think your switches may be too much for the the power supply, so the BS2p24 gets shut off. Try using the BS2p24 on a separate board and only sharing the Gnd and data lines.

Discovery

I solved the problem. One of the one-wire sensors required a strong 5 vdc power source so I connected the several foot long wire to the 5 vdc regulator on the BS2p24. When the solenoids activate or deactivate the EMI pulse is intercepted by the 5 vdc power line and sent directly into the micro controller thus stopping the processor. A separate 5 vdc power source was used to supply power to the sensor and all is well.

Sincerely,

Discovery

AwesomeCronk

Glad you solved it!

Discovery

Not so fast!
The observation that the problem was solved was an error...the BS2p24 program actually stopped when the solenoids activated. The solenoids fully engage in the first quarter cycle drawing about 10 amps on the 120 vac line which produces a powerful EMI pulse. What is interesting, is that the BS2e micro controller is not affected by the pulse as the two controllers are plugged into a wiring board. So, I began some experiments by adding 0.01 microfarad ceramic disk capacitors to the Vcc/Vee pins on both controllers. This had no affect. I added a 1.0 microfarad Mylar capacitor and 47 microfarad Tantalum capacitor from the 9 volt regulator rail to the ground rail with no change. I moved the BS2p24 to a separate plug-in wiring board using shielded coax 12 vdc power cables with no affect. I then machined a block of aluminum in which the BS2p24 plug-in board was placed. Coax fire-wall connectors were installed for the 12 vdc power and the One-wire signal interface. This grounded the entire aluminum block to the power supply and all sensors. Data wires were connected between the two controllers and this configuration worked properly. I did not expect the BS2p24 to be so sensitive to EMI.

So AwesomeCronk, you were in the right track.

Sincerely,

Discovery

AwesomeCronk

Wow. Interesting.

kwinn

These types of problems are the reason I like to use a zero crossing triac output opto-isolator followed by a rectifier to drive relay coils from an AC source whenever possible.

Discovery

Hi kwinn,

My configuration uses zero crossing triac opto-isolated electronic switches to drive the coils of the solenoids. Zero crossing detection is not the problem...the EMI pulse from the solenoid activation is the problem.

Sincerely,

Discovery

Discovery

The one missing item is the rectifier which would drive the solenoids. The cost of strong solenoids is ridiculously high and I have only 120 vac 60 Hz solenoids. You might be right using dc on the coils.

Sincerely,

Discovery

Discovery

One more thing...while running the system with only the BS2p24 shielded in the aluminum box, the DS1302 real-time clock malfunctioned outputting the wrong characters and stopping. As a result, I enclosed the BS2p24, the BS2e, and the DS1302 inside the shielded box. The system is running flawlessly for several days now.

Sincerely,

Discovery

AwesomeCronk

Huh, strange how the shielding works. Very glad it works now.

Discovery

Yes...so am I. A big headache solved.

Discovery

Discovery

Update. For over a month now the shielded controller that is described above continues to operate 24/7 without any problems. It is important to point out that the BS2p24, BS2e and the DS1302 are enclosed in a tight aluminum shell machined from a single block. All of the power and signal returns are tied to the aluminum block including one-wire coax and the DC power also delivered via a coax. High current 120 volt AC solenoids are energized and de-energized as controlling elements in the system. These solenoid devices are located within a few feet of the controller and must act very fast thus emitting a strong EMI pulse that, before enclosing the circuit devices in the shield, messed up the DS1302 clock and stopped the BS2p24 and BS2e micro controllers. If you have a system controlled by BS2 micro controllers running continuously that absolutely must not stop for any reason...consider a total shield as a solution.

Sincerely,

Discovery

DaveJenson

@Discovery
do you have some pictures you could share?

Discovery

Yes,
The first picture shows the machined aluminum enclosure with the coax cables attached to feed-thru connectors.
An output cable connects the aluminum enclosure circuits to the electronic switches shown in the second picture. The white cables interface with the solenoids. The interface cable does not require shielding.

Sincerely,

Discovery

Discovery

I first ran into the Electromagnetic pulse problem back around May 9th. The solution was to place all the processing chips in an aluminum enclosure. The enclosure was milled out of raw stock. Since placing the chips in the box, there have been no failures and the chips have run continuously. It is now September. I love it when a solution works.

Discovery

Cluso99

In the "old" days we used to put electronics in die cast boxes. Shielding was a necessary evil. Computer operators regularly crashed video terminals with static.