Hi All,
I have a 1940 Lister diesel charging set which uses various large solenoids and oil filled dash pots to control the startup sequence.
I was wondering if I could make a small circuit that could perform the startup and stop sequences. The start up sequence is something like.... Turn on fuel / engage starter contactor (approx 6 seconds) / switch over compression changeover valve / switch in generator contactor etc...
I found various 555 sequencer circuits on the internet, the 555 data and other bits of information and developed this circuit....
I started with one 555 timing an interval and just switching two LED's on and off.
I chose 12v as my voltage to work with as I can then switch relay coils on the output.
Then I added a second timer section and linked them to alternate between section 1 and section 2. It could have been more than 2 sections but all I wanted to do was prove it worked.
I then rummaged around to find a chunky transistor to switch the bigger loads. I found I had some TIP31A transistors and some TIP122 transistors. Looking at the data sheets the TIP122 seemed to have a much bigger gain so a small input and handling a big output.
That has a maximum 5v Base/Emitter voltage so I decided to add a potential divider from the output of the 555 to 0v to give about 4v for the TIP122 as the 555 output is 10.6v.
With the TIP122 connected Base / Emmiter voltage comes down to 1.4v over the transistor so maybe the potential divider is not needed but I left it in there to ensure the transistor did not see any more than 4v.
This is working well and I have been triggering a relay and another solenoid with it. This load is only about 0.5A so have not tried out getting the full 5A out of it yet.
The next problem I had with it was when I was using a piece of wire to cause a trigger on the first section, where my start switch now is, it would also trigger the second section. I tried a 100R resistor and that stopped it triggering both. I tried a 1.5K resistor and that also worked so I settled on a 1K resistor as I have more of those than any others.
I then tidied up my scrawled mess into the image above.
It would be great if some of the more knowledgeable folk on here could have a scan over the circuit to see if there is anything to comment on.
Rob
I have a 1940 Lister diesel charging set which uses various large solenoids and oil filled dash pots to control the startup sequence.
I was wondering if I could make a small circuit that could perform the startup and stop sequences. The start up sequence is something like.... Turn on fuel / engage starter contactor (approx 6 seconds) / switch over compression changeover valve / switch in generator contactor etc...
I found various 555 sequencer circuits on the internet, the 555 data and other bits of information and developed this circuit....


I started with one 555 timing an interval and just switching two LED's on and off.
I chose 12v as my voltage to work with as I can then switch relay coils on the output.
Then I added a second timer section and linked them to alternate between section 1 and section 2. It could have been more than 2 sections but all I wanted to do was prove it worked.
I then rummaged around to find a chunky transistor to switch the bigger loads. I found I had some TIP31A transistors and some TIP122 transistors. Looking at the data sheets the TIP122 seemed to have a much bigger gain so a small input and handling a big output.
That has a maximum 5v Base/Emitter voltage so I decided to add a potential divider from the output of the 555 to 0v to give about 4v for the TIP122 as the 555 output is 10.6v.
With the TIP122 connected Base / Emmiter voltage comes down to 1.4v over the transistor so maybe the potential divider is not needed but I left it in there to ensure the transistor did not see any more than 4v.
This is working well and I have been triggering a relay and another solenoid with it. This load is only about 0.5A so have not tried out getting the full 5A out of it yet.
The next problem I had with it was when I was using a piece of wire to cause a trigger on the first section, where my start switch now is, it would also trigger the second section. I tried a 100R resistor and that stopped it triggering both. I tried a 1.5K resistor and that also worked so I settled on a 1K resistor as I have more of those than any others.
I then tidied up my scrawled mess into the image above.
It would be great if some of the more knowledgeable folk on here could have a scan over the circuit to see if there is anything to comment on.
Rob
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