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I am interested in building a solenoid controller using latching type relays(containing 2 coils and DPDT). The relays are controlled using two momentary switches. The action I am looking to get is by pressing switch (SW1) I can have #1/4 solenoids activate, and by pressing SW1 again #2/4 solenoids activate while #1/4 deactivates. Pressing SW1 will activate each solenoid individually 1-4 in sequence till #4 is reached. SW2 will reverse the sequence direction from #4 to #1. Each press of either switch will control only one action respective to its purpose. Is this possible?

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  • \$\begingroup\$ I am sorry but I can't understand what you are asking. Maybe provide a sample sequence and reset conditions, something like: at reset all four solenoids are off, then you press SW1 and 3 goes on, you press it again and 2 goes on while 3 goes off... Something like that. \$\endgroup\$ – Vladimir Cravero Apr 24 '14 at 8:25
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    \$\begingroup\$ You mention both solenoids and relays. How are these connected together in your proposed circuit? \$\endgroup\$ – Chris Johnson Apr 24 '14 at 10:05
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I'd consider using a binary up-down counter like this. Decode the two least significant outputs with a 2-4 line decoder and then use 4x MOSFETs for driving the solenoids. Forget about latching relays - this is a more reliable solution I would say.

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  • \$\begingroup\$ Where it falls down is that it is volatile. If you use latching relays, removal and reapplication of power will not change which relay is active. \$\endgroup\$ – WhatRoughBeast Apr 24 '14 at 10:31
  • \$\begingroup\$ @WhatRoughBeast not if you use a small battery - it's cmos so it will last years. Who says this would be a problem anyway? \$\endgroup\$ – Andy aka Apr 24 '14 at 10:41
  • \$\begingroup\$ Nice solution -- will need debouncing on the pushbuttons though to avoid multiple counts on the same button press. \$\endgroup\$ – tcrosley Apr 24 '14 at 12:46
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The simplest way is to use a small microcontroller such as a 82-cent PIC16F1503 to debounce the switches and hold the current state in EEPROM, if necessary. If you want to use latching relays, the microcontroller could also generate output pulses (eg 50ms) to trigger the 8 coils, and power dissipation could thus be minimized.

It could be accomplished with logic packages but it would be rather tedious compared to a few lines of code.

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If you want to use both poles of each relay for driving solenoids, the answer is no. In general terms, the problem is that the coil drive from the switches must have information about the current state of the system, and that can only be determined (pretty much by definition) by accessing one or more of the relay contacts.

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  • \$\begingroup\$ But it is of course possible if the current state of the system could be stored in something other than the relay contacts (in an up/down counter, microcontroller, etc.). \$\endgroup\$ – Chris Johnson Apr 24 '14 at 10:40
  • \$\begingroup\$ Yes, of course. But it's clear that he wants do it with relays only. \$\endgroup\$ – WhatRoughBeast Apr 24 '14 at 15:26

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