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I have a 555 timer clock output controlling a few things, one of them is the coil of a 24v relay. How can I take the 5v coming from the 555 and pump it up to 24v. ?

schematic

simulate this circuit – Schematic created using CircuitLab

What I am doing is using the clock cycle to turn relay on/off . Then the 5v threw the contacts is being counted. Thus if I turn on off the relay 100 times, I should get 100 counts at the counter. The logic works for a 5v relay, but unsure how to change this for a 24v relay.

Thanks Glen

UPDATE Added circuit as suggested, now the relay will get 24v across coil when signal is high and 16v when signal is low(not low enough to turn off relay). Below is image of circuit. updated Circuit

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    \$\begingroup\$ Do you have a 24V power supply? Also, relays bounce, so your counter may be way off. \$\endgroup\$ – Trevor_G Nov 13 '17 at 19:21
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    \$\begingroup\$ You're not only trying to "pump up" the voltage, foremost you're trying to push more power through the relay coil than your 555 can supply. You'll need to switch a more powerful 24V supply, e.g. with a low-side switch in the shape of an NPN transistor or an n-channel MOSFET \$\endgroup\$ – Marcus Müller Nov 13 '17 at 19:23
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    \$\begingroup\$ ANd don't forget a flyback diode \$\endgroup\$ – Trevor_G Nov 13 '17 at 19:24
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    \$\begingroup\$ Like this i.stack.imgur.com/Tx4D1.jpg \$\endgroup\$ – Trevor_G Nov 13 '17 at 19:26
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    \$\begingroup\$ @Trevor so in this image VS is the 24v and the input to transistor would be the 555 clock. So simple, thanks for help! \$\endgroup\$ – user41758 Nov 13 '17 at 19:30
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If you really MUST use a 24V relay, or any relay really, you should use either an NPN or N-MOSFET driver like this..

schematic

simulate this circuit – Schematic created using CircuitLab

But that really is not the best way to clock a counter. Relays bounce and can cause your counter to miscount. I am assuming you are using a relay for reasons of isolation. As such using an opto-coupler would be better.

schematic

simulate this circuit

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  • \$\begingroup\$ The relay is what is being checked. the 555 , one path goes straight to counter, other goes threw relay to counter. I cycle it 99 times and make sure both counters are same , if not relay is sticking. For bounce, i added a RC circuit to contact side. \$\endgroup\$ – user41758 Nov 16 '17 at 18:01
  • \$\begingroup\$ Right now after trying this, I get at the relay coil 23volts when 555 signal is high, and 16 volts when its low. not sure why i get the 16volts when low.. But that 16 volts is enough to keep relay energized. Any thought on why there is 16 volts and not 0. \$\endgroup\$ – user41758 Nov 16 '17 at 18:03
  • \$\begingroup\$ 555 output may not be low enough. Using an n-mosfet would be better. \$\endgroup\$ – Trevor_G Nov 16 '17 at 18:17
  • \$\begingroup\$ @user41758 out of curiosity, what value did you chose for the base resistor. \$\endgroup\$ – Trevor_G Nov 16 '17 at 18:40
  • \$\begingroup\$ 1k resistor , i have a circuit of what i have now. But not sure if its ok to post it or not on original question. \$\endgroup\$ – user41758 Nov 16 '17 at 19:01

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