Can anyone help me with a ladder diagram to make a single light turn on for 5 seconds and then off for 5 seconds? I have mechanical timing and control relays. they are 120 volt coils, and are DPDT 8 pin cubes. I thought I could do it with just 2 timing relays, but I'm stumped, thinking I may need a CR in there somewhere to help it reset?
Blinker circuit using mechanical timing relays?
- Thread starter Rig84
- Start date
Barbqranch
Senior Member
- Location
- Arcata, CA
- Occupation
- Plant maintenance electrician Semi-retired
A single Omron H3CA-8 will do that. I like to always use them to control a second relay to handle the load, so as to preserve the timer's contacts.
They are quite cheap on eBay, and I have never had a failure with one from there.
They are quite cheap on eBay, and I have never had a failure with one from there.
Thanks for the tip on those H3CA-8's, that is something I could look into, but I'm really hoping to find some help with the ladder diagram for the relays I have. It's been driving me nuts the last few days
wwhitney
Senior Member
- Location
- Berkeley, CA
- Occupation
- Retired
I'm not super familiar with this product space, can you clarify what functions your existing relay implement? This web page lists a variety of possible functions for timer relays:
- On-delay - after application of the input voltage and the user-defined time delay expires, the output is energized
- Off-delay - upon application of the input voltage, the output is energized. When the input voltage is removed and the user-defined time delay expires, the output is de-energized
- On-delay flasher - operates the same as the On Delay relay but with an oscillating output that switches on and off at a user-defined interval
- On-interval - upon application of input voltage, the output is energized and stays energized until the user-defined time delay expires
- Single shot - once the input voltage is applied, the relay waits for a trigger. Once triggered, the output is energized and stays energized until the user-defined time delay expires. This process will start again with any trigger received while the input voltage is present.
- Cyclic (repeat cycle) - when the input voltage is applied, a user-defined time delay begins. At the end of this delay, the output is energized for a second user-defined time interval. At the end of the second interval, the output is de-energized and the sequence repeats until input voltage is removed.
Thanks,
Wayne
zbang
Senior Member
- Location
- Roughly 5346 miles from Earls Court
For questions like this, it helps to include some info about which relays you already have.
Hi Wayne, thanks for the reply, The relays I have are square D electrical timing relays. They are 8 pin DPDT on delay with a 120 volt coil. I'm trying to get them to light a single LED for 5 seconds, then turn off 5 seconds and repeat. years ago I did a circuit for a Halloween prop using this same on/off/repeat, using these things, I just can't remember how I did it. I know I used 2 timing relays, but I'm now thinking I might've used a cube relay in there somewhere as well.
The relays I have are square D electrical timing relays. They are 8 pin DPDT on delay with a 120 volt coil
wwhitney
Senior Member
- Location
- Berkeley, CA
- Occupation
- Retired
OK, I think that DPDT on delay relay means this (sorry if my terminology is non-standard, not in this field):
2 coil pins X/Y
2 sets of 3 pins NC/C/NO
If the coil pins X/Y have been powered at least T seconds (T configurable), then in each of the 2 sets of contacts C is connected to NO. Otherwise C is connected to NC.
In that case, you can do what you want. I'm not familiar with ladder diagrams, but the idea is:
Power goes through normally closed contacts of relay 2 to the coil of relay 1 and to one side of the normally open contacts of relay 1. Then from the other side of those normally open contacts of relay 1, it goes to the load and to the coil of relay 2.
So when you energize the circuit, relay coil 1 gets power. 5 seconds later, relay 1 causes the load and relay coil 2 to get power. 5 seconds later, relay 2 causes the power to relay coil 1 to get interrupted. That in turn interrupts power to relay coil 2, so it reverts and relay coil 1 gets power again, repeating the cycle.
Cheers, Wayne
2 coil pins X/Y
2 sets of 3 pins NC/C/NO
If the coil pins X/Y have been powered at least T seconds (T configurable), then in each of the 2 sets of contacts C is connected to NO. Otherwise C is connected to NC.
In that case, you can do what you want. I'm not familiar with ladder diagrams, but the idea is:
Power goes through normally closed contacts of relay 2 to the coil of relay 1 and to one side of the normally open contacts of relay 1. Then from the other side of those normally open contacts of relay 1, it goes to the load and to the coil of relay 2.
So when you energize the circuit, relay coil 1 gets power. 5 seconds later, relay 1 causes the load and relay coil 2 to get power. 5 seconds later, relay 2 causes the power to relay coil 1 to get interrupted. That in turn interrupts power to relay coil 2, so it reverts and relay coil 1 gets power again, repeating the cycle.
Cheers, Wayne
kwired
Electron manager
- Location
- NE Nebraska
Here is how you can do it with two basic on delay relays, could even be single pole double throw timing relays and could still work though most will be double pole.
Load is on while T1 is timing, off while T2 is timing. cycle resets when T2 is done timing.
Load is on while T1 is timing, off while T2 is timing. cycle resets when T2 is done timing.
Lifesaver! Thank you for the detailed explanation! I feel like an idiot for not getting this on my own.
Like I just told Wayne, thank you for your help! The ladder helped greatly. I can't believe I couldn't get this. I guess I was over thinking it.
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
Part numbers could help us look up your actual terminal numbers, but I think you have what you need.