MK125 project kit ldr kit

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1

hi

i have bought this kit and works fine But i want to get rid of the time delay. i noticed when i switch the circuit on in the dark it has a time delay before the relay is triggered which is no good for my design. i know this was put in so the relay does not keep going on/off but that does not matter to me. i am using it in a car so the power is only triggered then car door opens but relay takes too long to trigger in the dark for my led lights to come on. i want them to come on stright away when its dark and when circuit is powered.

i hope you can help save me making my circuit with transistor and pd circuit. i work for maplin electronics and we sell alot of you products as well. i fairly sure all i need to do is just remove the capicator but please let me know what i need to do

thanks

jay.

2

Remove the capacitor.

3

do i also need to remove the resistor ? r4 seems to look like that is for the cap c3 which i will be removing. or does not matter?

4

No need to remove resistor.

5

I am grateful to learn of this fix in order to remove the design delay. I, too, need the circuit to operate with no delay. But you are way ahead of me in understanding, so here are two newby questions, so I don’t ruin my kit;
May I assume that the capacitor to be removed is C2, not either of the electrolytic capacitors C1, or C3? Jaypat seems to be removing C3
May I further assume that I need to jumper between the two now-empty holes in the circuit board that were meant for the two pins of C2?
Thank you for your answers, and please forgive my ignorance.
lazycreeks

6

if i was you just get a very small cap and stick it in.

7

Thanks to jaypat. My project required a circuit that can respond with no delay, and
also that the circuit turn on in the presence of light, and turn off when it’s dark.
The suggestions to remove C3, substituting a low value capacitor, and swapping
IC pins 12 and 13 accomplished both of these modifications. The circuit works
flawlessly, and we are shocked at how sensitive the LDR is. One other thing I did
was to coat the LDR with silicone and let it dry 24 hours (to reduce degradation of
the LDR in the presence of humidity)
These changes were all that were required to make this circuit adapted to my needs.
Thanks to Velleman for a solid circuit, and to all the posters who wrote on these modifications.

8

no problem