Re: [CAD_CAM_EDM_DRO] Re: I need a latching relay...or do I?

Use a relay with three or four contacts then...use one of the extra sets of
contacts to "self latch" the relay. All you need to do is connect a N.O.
set of relay contacts across (in parallel with) the foot switch.

Smoke

>Smoke,
>
>Yes, your setup will work, but for this project I need to latch the
>relay so I don't have to keep my foot on the pedal.
>
>I'm implementing the first step in automation of a cut off saw. It's
>a Dake cold saw where the operator manually downfeeds it with a long
>handle. With the automatic downfeed and return there'll be time to
>debur or other operations on the last part cutoff. Plus, on this
>type of saw you get better blade life with a consistent feed rate.
>
>I got the inspiration for this modification at a tool show I attended
>yesterday, Dake showed a saw nearly identical to mine with the
>hydraulic feed. Next step will be some sort of bar feeder mechanism
>for total automatic operation.
>
>thanks,
>
>Doug
>
>-- In CAD_CAM_EDM_DRO@y..., gordonr@r... wrote:
>> Yes, there is a much simpler way. All you need is a relay with two
>sets of
>> contacts..one N.O. & one N.C., the foot switch and two N.C. limit
>switches.
>>
>> Wire the foot switch and one limit switch in series with the relay.
>>
>> Wire the N.O. set of relay contacts in series with the Fwd
>solenoid.
>> Wire the N.C. set of contacts and the other limit switch in series
>with the Rev.
>> solenoid.
>>
>> The system will operate as follows:
>> Depress the foot switch and the relay will energize. The N.O.
>contacts will
>> close energizing the Fwd solenoid while the N.C. contacts will open
>ensuring the
>> Rev. soleniod remains de-energized. When the ram stroke reaches
>its forward
>> limit, the limit switch will open and de-energize the relay. The
>Fwd solenoid
>> will de-energize while the Rev solenoid energizes causing the
>required reverse
>> motion.
>>
>> When the ram reaches the reverse home postion , the extra limit
>switch will open
>> and cause the system to stop.
>>
>> During any forward motion, the foot switch must be held down...a
>good safety
>> precaution in case you need an "instant reverse"
>>
>> You can also put in an emergency stop button to cause all
>motion...forward and
>> reverse to cease.
>>
>> Smoke
>>
>> Smoke
>>
>
>
>
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