# Help with Velleman MK111 !!

Discussion in 'The Projects Forum' started by titjaune, Jan 13, 2012.

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1. ### titjaune Thread Starter New Member

Jan 13, 2012
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Digging out this topic...

Hello everybody, I'm a french newcomer here and have no serious knowledge about electronic circuits and components...
However, I'd like to know if I may modify the MK111 with a capacitor to let the 555 and it's relay working (for 1 second or 2) when I stop +12V DC on "screw 2" ?
If so, what would be the new capacitor value ?
Should I have to change "D3" ?
Here is a pic.

Note : the checked consumption is about 50mA NC and 9mA NO, frequency about 1Hz

Last edited: Jan 13, 2012

Dec 26, 2010
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Unfortunately your link to a picture does not work. From Bertus's diagram, the +12V is applied to terminal 1 (or pin1) of J1, and ground to terminal 2 (or pin 2).

(I don't know if J1 is a screw terminal block, or a plug / socket with pins, but even if the connections are screws we don't generally call them that. Usually a screw = "un vis", but it has other meanings, best avoided in accidental reference ")

If you hope to hold on the relay for a couple of seconds, you may need quite a big capacitor. Do you know the relay coil current?

The capacitor value may be estimated from C = I.T/(V1-V2), where I is the total circuit supply current, likely dominated by that of the relay, V1 is the initial voltage, and V2 is the highest voltage at which the relay is likely to drop out. NB D3 and the 555 and drop some voltage, which needs to be allowed for in working out V1 1nd V2.

The capacitor is likely to be quite large. Suppose we try some ballpark figures: let's take (V1-V2)=5V, T =2s, I = 40mA, we get C = 0.016F or 16000μF.

Note that if the incoming voltage is going to be forced down rather than disconnected, the new capacitor would need to be connected after D3, not at the J1 input. D1 could then face a severe current surge on connection of the supply. Are you certain that there is not some less brutal way of doing this?

3. ### titjaune Thread Starter New Member

Jan 13, 2012
5
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Oops, we switched our messages and edit :
"Note : the checked consumption is about 50mA NC and 9mA NO, frequency about 1H"

Dec 26, 2010
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That capacitor is going to have to be pretty big then: some tens of thousands of microfarads.

Note that although extremely compact high value capacitors are now available, some are limited to around 5V, and are only able to deliver very small currents.

What are you actually trying to do? There may be a better way around this.

5. ### titjaune Thread Starter New Member

Jan 13, 2012
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Well... I bought from a eBay seller some "switchback leds" to put in corner blinkers of my wife's Suzuki Jimny. (1157 base white & amber)
Unfortunately they came in "type 1" but I expected "type 2" ones : the difference between 1 & 2 is about the state of white leds during amber blinking : 1 "white, amber, white, amber, white..." and 2 "white, amber, off, amber, off, amber, off..., white"
I'd like to make white leds staying off during amber is blinking.
Thats why my local electronic parts retailer sold me a MK111 named "delayed relay".... but with only one entry signal and one NO/NC output : the perfect circuit should have two entry (white day running lights and amber blinking corner lights).
Forgive my approximative English if syntax is not correct...

6. ### titjaune Thread Starter New Member

Jan 13, 2012
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I try again to attach a pic

• ###### Photo72''.jpg
File size:
188.2 KB
Views:
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Dec 26, 2010
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The problem is not so much the syntax as the subject matter. Unfortunately it is a rule of this forum that automotive subjects are not discussed - and it's pretty thoroughly enforced.

We can probably expect intervention from the moderators some time soon, but even if I were allowed to discuss such subjects I really would not recommend trying anything as kludgey (British : bodged) (French: rafistolé?).

If I were you, I would go back to the dealer and get the right parts.

8. ### titjaune Thread Starter New Member

Jan 13, 2012
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Sorry, i didn't know about that...
But you know, the DRL has just become compulsory in France and a solution to stay legal is to install them in indicators.
My modification simply aims at making the change of color more visible for more safety...
Considering the MK111 for itself, is my proposition (in red on my picture) correct to keep the relay "on" for a fraction of a second ?
P.S. : I'm 40 years old and don't want to modify a car to make it dangerous or something : my son regularly sits behind this car and I want to keep him alive!
This web site is the more reactive and the first in Google search to fix such a problem

Last edited: Jan 13, 2012
9. ### Georacer Moderator

Nov 25, 2009
5,151
1,266
Unfortunately, we cannot help you in this matter. The forum rules exclude any automotive modification for the moment.